prefetch: Enable thumbnail fetching with feed

Article thumbnails are now fetched for suggestions from feed.
We fetch with the cached image fetcher, which is shared with feed.

Bug: 841522
Change-Id: I283fa2ea145341fb28dd337026a57abbd36aec77
Reviewed-on: https://chromium-review.googlesource.com/c/1344549
Commit-Queue: Dan H <harringtond@google.com>
Reviewed-by: Martin Šrámek <msramek@chromium.org>
Reviewed-by: Filip Gorski <fgorski@chromium.org>
Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612814}

chrome/browser/offline_pages/prefetch/prefetch_service_factory.cc

@@ -11,6 +11,7 @@
 #include "base/memory/singleton.h"
 #include "base/sequenced_task_runner.h"
 #include "base/task/post_task.h"
+#include "chrome/browser/cached_image_fetcher/cached_image_fetcher_service_factory.h"
 #include "chrome/browser/download/download_service_factory.h"
 #include "chrome/browser/ntp_snippets/content_suggestions_service_factory.h"
 #include "chrome/browser/offline_pages/offline_page_model_factory.h"
@@ -23,6 +24,9 @@
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_content_client.h"
 #include "components/feed/feed_feature_list.h"
+#include "components/image_fetcher/core/cached_image_fetcher.h"
+#include "components/image_fetcher/core/cached_image_fetcher_service.h"
+#include "components/image_fetcher/core/image_fetcher_impl.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h"
 #include "components/offline_pages/core/prefetch/prefetch_downloader_impl.h"
@@ -43,6 +47,7 @@ PrefetchServiceFactory::PrefetchServiceFactory()
           BrowserContextDependencyManager::GetInstance()) {
   DependsOn(DownloadServiceFactory::GetInstance());
   DependsOn(OfflinePageModelFactory::GetInstance());
+  DependsOn(image_fetcher::CachedImageFetcherServiceFactory::GetInstance());
 }
 
 // static
@@ -61,7 +66,6 @@ KeyedService* PrefetchServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   const bool feed_enabled =
       base::FeatureList::IsEnabled(feed::kInterestFeedContentSuggestions);
-
   Profile* profile = Profile::FromBrowserContext(context);
   DCHECK(profile);
   OfflinePageModel* offline_page_model =
@@ -93,9 +97,17 @@ KeyedService* PrefetchServiceFactory::BuildServiceInstanceFor(
   // Conditional components for Zine. Not created when using Feed.
   std::unique_ptr<SuggestedArticlesObserver> suggested_articles_observer;
   std::unique_ptr<ThumbnailFetcherImpl> thumbnail_fetcher;
+  // Conditional components for Feed. Not created when using Zine.
+  std::unique_ptr<image_fetcher::ImageFetcher> thumbnail_image_fetcher;
   if (!feed_enabled) {
     suggested_articles_observer = std::make_unique<SuggestedArticlesObserver>();
     thumbnail_fetcher = std::make_unique<ThumbnailFetcherImpl>();
+  } else {
+    image_fetcher::CachedImageFetcherService* image_fetcher_service =
+        image_fetcher::CachedImageFetcherServiceFactory::GetForBrowserContext(
+            context);
+    DCHECK(image_fetcher_service);
+    thumbnail_image_fetcher = image_fetcher_service->CreateCachedImageFetcher();
   }
 
   auto prefetch_downloader = std::make_unique<PrefetchDownloaderImpl>(
@@ -114,8 +126,8 @@ KeyedService* PrefetchServiceFactory::BuildServiceInstanceFor(
       std::move(prefetch_network_request_factory), offline_page_model,
       std::move(prefetch_store), std::move(suggested_articles_observer),
       std::move(prefetch_downloader), std::move(prefetch_importer),
-      std::move(prefetch_background_task_handler),
-      std::move(thumbnail_fetcher));
+      std::move(prefetch_background_task_handler), std::move(thumbnail_fetcher),
+      std::move(thumbnail_image_fetcher));
 }
 
 }  // namespace offline_pages

components/offline_pages/core/offline_page_model.h

@@ -19,8 +19,7 @@
 #include "components/offline_pages/core/offline_page_archiver.h"
 #include "components/offline_pages/core/offline_page_thumbnail.h"
 #include "components/offline_pages/core/offline_page_types.h"
-
-class GURL;
+#include "url/gurl.h"
 
 namespace offline_pages {
 

components/offline_pages/core/prefetch/BUILD.gn

@@ -74,6 +74,8 @@ static_library("prefetch") {
     "tasks/generate_page_bundle_task.h",
     "tasks/get_operation_task.cc",
     "tasks/get_operation_task.h",
+    "tasks/get_thumbnail_info_task.cc",
+    "tasks/get_thumbnail_info_task.h",
     "tasks/import_archives_task.cc",
     "tasks/import_archives_task.h",
     "tasks/import_cleanup_task.cc",
@@ -90,6 +92,8 @@ static_library("prefetch") {
     "tasks/sent_get_operation_cleanup_task.h",
     "tasks/stale_entry_finalizer_task.cc",
     "tasks/stale_entry_finalizer_task.h",
+    "thumbnail_fetch_by_url.cc",
+    "thumbnail_fetch_by_url.h",
     "thumbnail_fetcher.h",
   ]
 
@@ -102,6 +106,7 @@ static_library("prefetch") {
     "//components/download/public/background_service:public",
     "//components/gcm_driver",
     "//components/gcm_driver/common",
+    "//components/image_fetcher/core",
     "//components/keyed_service/core",
     "//components/ntp_snippets",
     "//components/offline_pages/core",
@@ -163,6 +168,7 @@ static_library("test_support") {
     "//components/download/public/background_service:public",
     "//components/download/public/background_service/test:test_support",
     "//components/gcm_driver/instance_id",
+    "//components/image_fetcher/core:test_support",
     "//components/keyed_service/core",
     "//components/offline_pages/core",
     "//components/offline_pages/core:switches",
@@ -227,6 +233,7 @@ source_set("unit_tests") {
     "tasks/generate_page_bundle_reconcile_task_unittest.cc",
     "tasks/generate_page_bundle_task_unittest.cc",
     "tasks/get_operation_task_unittest.cc",
+    "tasks/get_thumbnail_info_task_unittest.cc",
     "tasks/import_archives_task_unittest.cc",
     "tasks/import_cleanup_task_unittest.cc",
     "tasks/import_completed_task_unittest.cc",
@@ -245,6 +252,7 @@ source_set("unit_tests") {
     "//components/download/public/background_service:public",
     "//components/download/public/background_service/test:test_support",
     "//components/gcm_driver/instance_id",
+    "//components/image_fetcher/core:test_support",
     "//components/offline_pages/core",
     "//components/offline_pages/core:switches",
     "//components/offline_pages/core:test_support",

components/offline_pages/core/prefetch/DEPS

 include_rules = [
   "+components/download/internal/test",
   "+components/download/public",
-  "+components/prefs",
-  "+google_apis",
-  "+components/variations",
   "+components/gcm_driver",
+  "+components/image_fetcher",
   "+components/ntp_snippets",
+  "+components/prefs",
+  "+components/variations",
   "+components/version_info",
+  "+google_apis",
   "+net",
   "+services/network/public/cpp",
   "+services/network/test",

components/offline_pages/core/prefetch/prefetch_dispatcher_impl.cc

@@ -45,6 +45,7 @@
 #include "components/offline_pages/core/prefetch/tasks/page_bundle_update_task.h"
 #include "components/offline_pages/core/prefetch/tasks/sent_get_operation_cleanup_task.h"
 #include "components/offline_pages/core/prefetch/tasks/stale_entry_finalizer_task.h"
+#include "components/offline_pages/core/prefetch/thumbnail_fetch_by_url.h"
 #include "components/offline_pages/core/prefetch/thumbnail_fetcher.h"
 #include "components/prefs/pref_service.h"
 #include "url/gurl.h"
@@ -58,8 +59,10 @@ void DeleteBackgroundTaskHelper(std::unique_ptr<PrefetchBackgroundTask> task) {
 }
 
 PrefetchURL SuggestionToPrefetchURL(PrefetchSuggestion suggestion) {
-  return PrefetchURL(suggestion.article_url.spec(), suggestion.article_url,
+  PrefetchURL result(suggestion.article_url.spec(), suggestion.article_url,
                      base::UTF8ToUTF16(suggestion.article_title));
+  result.thumbnail_url = suggestion.thumbnail_url;
+  return result;
 }
 
 }  // namespace
@@ -125,8 +128,8 @@ void PrefetchDispatcherImpl::NewSuggestionsAvailable(
     SuggestionsProvider* suggestions_provider) {
   if (!prefetch_prefs::IsEnabled(pref_service_))
     return;
-  suggestions_provider->GetCurrentArticleSuggestions(base::BindOnce(
-      &PrefetchDispatcherImpl::AddSuggestions, weak_factory_.GetWeakPtr()));
+  suggestions_provider->GetCurrentArticleSuggestions(
+      base::BindOnce(&PrefetchDispatcherImpl::AddSuggestions, GetWeakPtr()));
 }
 
 void PrefetchDispatcherImpl::RemoveSuggestion(const GURL& url) {
@@ -233,7 +236,7 @@ void PrefetchDispatcherImpl::QueueActionTasks() {
       service_->GetPrefetchNetworkRequestFactory(),
       base::BindOnce(
           &PrefetchDispatcherImpl::DidGenerateBundleOrGetOperationRequest,
-          weak_factory_.GetWeakPtr(), "GetOperationRequest"));
+          GetWeakPtr(), "GetOperationRequest"));
   task_queue_.AddTask(std::move(get_operation_task));
 
   std::unique_ptr<Task> generate_page_bundle_task =
@@ -242,7 +245,7 @@ void PrefetchDispatcherImpl::QueueActionTasks() {
           service_->GetPrefetchNetworkRequestFactory(),
           base::BindOnce(
               &PrefetchDispatcherImpl::DidGenerateBundleOrGetOperationRequest,
-              weak_factory_.GetWeakPtr(), "GeneratePageBundleRequest"));
+              GetWeakPtr(), "GeneratePageBundleRequest"));
   task_queue_.AddTask(std::move(generate_page_bundle_task));
 }
 
@@ -428,11 +431,6 @@ void PrefetchDispatcherImpl::FetchThumbnails(
   if (remaining_ids->empty())
     return;
 
-  // Zine/Feed
-  // TODO(https://crbug.com/841516): Implement thumbnail fetching with the Feed.
-  if (!service_->GetThumbnailFetcher())
-    return;
-
   int64_t offline_id = remaining_ids->back().first;
   ClientId client_id = std::move(remaining_ids->back().second);
   DCHECK(client_id.name_space == kSuggestedArticlesNamespace);
@@ -441,7 +439,7 @@ void PrefetchDispatcherImpl::FetchThumbnails(
   service_->GetOfflinePageModel()->HasThumbnailForOfflineId(
       offline_id,
       base::BindOnce(&PrefetchDispatcherImpl::ThumbnailExistenceChecked,
-                     base::Unretained(this), offline_id, std::move(client_id),
+                     GetWeakPtr(), offline_id, std::move(client_id),
                      std::move(remaining_ids), is_first_attempt));
 }
 
@@ -454,12 +452,38 @@ void PrefetchDispatcherImpl::ThumbnailExistenceChecked(
   if (thumbnail_exists) {
     FetchThumbnails(std::move(remaining_ids), is_first_attempt);
   } else {
-    auto complete_callback = base::BindOnce(
-        &PrefetchDispatcherImpl::ThumbnailFetchComplete, base::Unretained(this),
-        offline_id, std::move(remaining_ids), is_first_attempt);
-    service_->GetThumbnailFetcher()->FetchSuggestionImageData(
-        client_id, is_first_attempt, std::move(complete_callback));
+    // Zine/Feed: thumbnail_fetcher is non-null only with Zine.
+    ThumbnailFetcher* thumbnail_fetcher = service_->GetThumbnailFetcher();
+    if (thumbnail_fetcher) {
+      auto complete_callback = base::BindOnce(
+          &PrefetchDispatcherImpl::ThumbnailFetchComplete, GetWeakPtr(),
+          offline_id, std::move(remaining_ids), is_first_attempt);
+      thumbnail_fetcher->FetchSuggestionImageData(client_id, is_first_attempt,
+                                                  std::move(complete_callback));
+    } else {
+      task_queue_.AddTask(std::make_unique<GetThumbnailInfoTask>(
+          service_->GetPrefetchStore(), offline_id,
+          base::BindOnce(&PrefetchDispatcherImpl::ThumbnailInfoReceived,
+                         GetWeakPtr(), offline_id, std::move(remaining_ids),
+                         is_first_attempt)));
+    }
+  }
+}
+
+void PrefetchDispatcherImpl::ThumbnailInfoReceived(
+    const int64_t offline_id,
+    std::unique_ptr<IdsVector> remaining_ids,
+    bool is_first_attempt,
+    GetThumbnailInfoTask::Result result) {
+  if (result.thumbnail_url.is_empty()) {
+    FetchThumbnails(std::move(remaining_ids), is_first_attempt);
+    return;  // No thumbnail url was given to us for this page.
   }
+  FetchThumbnailByURL(
+      base::BindOnce(&PrefetchDispatcherImpl::ThumbnailFetchComplete,
+                     GetWeakPtr(), offline_id, std::move(remaining_ids),
+                     is_first_attempt),
+      service_->GetThumbnailImageFetcher(), result.thumbnail_url);
 }
 
 void PrefetchDispatcherImpl::ThumbnailFetchComplete(

components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h

@@ -15,6 +15,8 @@
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "components/offline_pages/core/prefetch/prefetch_dispatcher.h"
+#include "components/offline_pages/core/prefetch/suggestions_provider.h"
+#include "components/offline_pages/core/prefetch/tasks/get_thumbnail_info_task.h"
 #include "components/offline_pages/task/task_queue.h"
 #include "components/version_info/channel.h"
 #include "net/url_request/url_request_context_getter.h"
@@ -64,6 +66,10 @@ class PrefetchDispatcherImpl : public PrefetchDispatcher,
  private:
   friend class PrefetchDispatcherTest;
 
+  base::WeakPtr<PrefetchDispatcherImpl> GetWeakPtr() {
+    return weak_factory_.GetWeakPtr();
+  }
+
   void DisposeTask();
 
   // Callbacks for network requests.
@@ -112,6 +118,10 @@ class PrefetchDispatcherImpl : public PrefetchDispatcher,
                                  std::unique_ptr<IdsVector> remaining_ids,
                                  bool is_first_attempt,
                                  bool thumbnail_exists);
+  void ThumbnailInfoReceived(const int64_t offline_id,
+                             std::unique_ptr<IdsVector> remaining_ids,
+                             bool is_first_attempt,
+                             GetThumbnailInfoTask::Result result);
   void ThumbnailFetchComplete(const int64_t offline_id,
                               std::unique_ptr<IdsVector> remaining_ids,
                               bool is_first_attempt,

components/offline_pages/core/prefetch/prefetch_downloader_impl.cc

@@ -96,10 +96,9 @@ void PrefetchDownloaderImpl::StartDownload(const std::string& download_id,
         policy {
           cookies_allowed: NO
           setting:
-            "Users can enable or disable the offline prefetch on desktop by "
-            "toggling 'Use a prediction service to load pages more quickly' in "
-            "settings under Privacy and security, or on Android by toggling "
-            "chrome://flags#offline-prefetch."
+            "Users can enable or disable offline prefetch by toggling "
+            "'Download articles for you' in settings under Downloads or "
+            "by toggling chrome://flags#offline-prefetch."
           chrome_policy {
             NetworkPredictionOptions {
               NetworkPredictionOptions: 2

components/offline_pages/core/prefetch/prefetch_item.h

@@ -22,6 +22,8 @@ namespace offline_pages {
 // successfully or not.
 // Instances of this class are in-memory representations of items in (or to be
 // inserted into) the persistent prefetching data store.
+//
+// Only used in tests.
 struct PrefetchItem {
   PrefetchItem();
   PrefetchItem(PrefetchItem&& other);

components/offline_pages/core/prefetch/prefetch_request_fetcher.cc

@@ -68,8 +68,9 @@ PrefetchRequestFetcher::PrefetchRequestFetcher(
         policy {
           cookies_allowed: NO
           setting:
-            "Users can enable or disable the offline prefetch by toggling"
-            "chrome://flags#offline-prefetch in Chromium on Android."
+            "Users can enable or disable offline prefetch by toggling "
+            "'Download articles for you' in settings under Downloads or "
+            "by toggling chrome://flags#offline-prefetch."
           policy_exception_justification:
             "Not implemented, considered not useful."
         })");

components/offline_pages/core/prefetch/prefetch_service.h

@@ -9,6 +9,9 @@
 
 class GURL;
 
+namespace image_fetcher {
+class ImageFetcher;
+}
 namespace ntp_snippets {
 class ContentSuggestionsService;
 }
@@ -92,6 +95,7 @@ class PrefetchService : public KeyedService {
   // Zine/Feed: Null when using the Feed.
   virtual ThumbnailFetcher* GetThumbnailFetcher() = 0;
   virtual OfflinePageModel* GetOfflinePageModel() = 0;
+  virtual image_fetcher::ImageFetcher* GetThumbnailImageFetcher() = 0;
 
   // Test-only methods.
 

components/offline_pages/core/prefetch/prefetch_service_impl.cc

@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/logging.h"
+#include "components/image_fetcher/core/image_fetcher.h"
 #include "components/offline_pages/core/client_id.h"
 #include "components/offline_pages/core/client_namespace_constants.h"
 #include "components/offline_pages/core/prefetch/offline_metrics_collector.h"
@@ -36,7 +37,8 @@ PrefetchServiceImpl::PrefetchServiceImpl(
     std::unique_ptr<PrefetchImporter> prefetch_importer,
     std::unique_ptr<PrefetchBackgroundTaskHandler>
         prefetch_background_task_handler,
-    std::unique_ptr<ThumbnailFetcher> thumbnail_fetcher)
+    std::unique_ptr<ThumbnailFetcher> thumbnail_fetcher,
+    std::unique_ptr<image_fetcher::ImageFetcher> thumbnail_image_fetcher)
     : offline_metrics_collector_(std::move(offline_metrics_collector)),
       prefetch_dispatcher_(std::move(dispatcher)),
       prefetch_gcm_handler_(std::move(gcm_handler)),
@@ -48,7 +50,8 @@ PrefetchServiceImpl::PrefetchServiceImpl(
       prefetch_background_task_handler_(
           std::move(prefetch_background_task_handler)),
       suggested_articles_observer_(std::move(suggested_articles_observer)),
-      thumbnail_fetcher_(std::move(thumbnail_fetcher)) {
+      thumbnail_fetcher_(std::move(thumbnail_fetcher)),
+      thumbnail_image_fetcher_(std::move(thumbnail_image_fetcher)) {
   prefetch_dispatcher_->SetService(this);
   prefetch_downloader_->SetPrefetchService(this);
   prefetch_gcm_handler_->SetService(this);
@@ -73,6 +76,7 @@ void PrefetchServiceImpl::SetContentSuggestionsService(
   DCHECK(suggested_articles_observer_);
   DCHECK(!suggestions_provider_);
   DCHECK(thumbnail_fetcher_);
+  DCHECK(!thumbnail_image_fetcher_);
   suggested_articles_observer_->SetContentSuggestionsServiceAndObserve(
       content_suggestions);
   thumbnail_fetcher_->SetContentSuggestionsService(content_suggestions);
@@ -82,6 +86,7 @@ void PrefetchServiceImpl::SetSuggestionProvider(
     SuggestionsProvider* suggestions_provider) {
   DCHECK(!suggested_articles_observer_);
   DCHECK(!thumbnail_fetcher_);
+  DCHECK(thumbnail_image_fetcher_);
   suggestions_provider_ = suggestions_provider;
 }
 
@@ -146,6 +151,10 @@ ThumbnailFetcher* PrefetchServiceImpl::GetThumbnailFetcher() {
   return thumbnail_fetcher_.get();
 }
 
+image_fetcher::ImageFetcher* PrefetchServiceImpl::GetThumbnailImageFetcher() {
+  return thumbnail_image_fetcher_.get();
+}
+
 void PrefetchServiceImpl::Shutdown() {
   suggested_articles_observer_.reset();
   prefetch_downloader_.reset();

components/offline_pages/core/prefetch/prefetch_service_impl.h

@@ -30,7 +30,8 @@ class PrefetchServiceImpl : public PrefetchService {
       std::unique_ptr<PrefetchDownloader> prefetch_downloader,
       std::unique_ptr<PrefetchImporter> prefetch_importer,
       std::unique_ptr<PrefetchBackgroundTaskHandler> background_task_handler,
-      std::unique_ptr<ThumbnailFetcher> thumbnail_fetcher);
+      std::unique_ptr<ThumbnailFetcher> thumbnail_fetcher,
+      std::unique_ptr<image_fetcher::ImageFetcher> thumbnail_image_fetcher_);
 
   ~PrefetchServiceImpl() override;
 
@@ -54,9 +55,14 @@ class PrefetchServiceImpl : public PrefetchService {
   PrefetchDownloader* GetPrefetchDownloader() override;
   PrefetchImporter* GetPrefetchImporter() override;
   PrefetchBackgroundTaskHandler* GetPrefetchBackgroundTaskHandler() override;
+
+  // Thumbnail fetchers. With Feed, GetThumbnailImageFetcher() is available
+  // and GetThumbnailFetcher() is null.
   ThumbnailFetcher* GetThumbnailFetcher() override;
+  image_fetcher::ImageFetcher* GetThumbnailImageFetcher() override;
 
   SuggestedArticlesObserver* GetSuggestedArticlesObserverForTesting() override;
+
   // KeyedService implementation:
   void Shutdown() override;
 
@@ -77,6 +83,7 @@ class PrefetchServiceImpl : public PrefetchService {
   // Zine/Feed: only non-null when using Zine.
   std::unique_ptr<SuggestedArticlesObserver> suggested_articles_observer_;
   std::unique_ptr<ThumbnailFetcher> thumbnail_fetcher_;
+  std::unique_ptr<image_fetcher::ImageFetcher> thumbnail_image_fetcher_;
 
   // Zine/Feed: only non-null when using Feed.
   SuggestionsProvider* suggestions_provider_ = nullptr;

components/offline_pages/core/prefetch/prefetch_service_test_taco.cc

@@ -9,6 +9,8 @@
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "components/image_fetcher/core/image_fetcher.h"
+#include "components/image_fetcher/core/mock_image_fetcher.h"
 #include "components/offline_pages/core/offline_page_model.h"
 #include "components/offline_pages/core/prefetch/mock_thumbnail_fetcher.h"
 #include "components/offline_pages/core/prefetch/offline_metrics_collector.h"
@@ -79,6 +81,9 @@ PrefetchServiceTestTaco::PrefetchServiceTestTaco(SuggestionSource source) {
     // result here.  This allows us to not create a ContentSuggestionsService.
     suggested_articles_observer_->GetTestingArticles();
     thumbnail_fetcher_ = std::make_unique<MockThumbnailFetcher>();
+  } else {
+    thumbnail_image_fetcher_ =
+        std::make_unique<image_fetcher::MockImageFetcher>();
   }
 
   prefetch_background_task_handler_ =
@@ -156,6 +161,12 @@ void PrefetchServiceTestTaco::SetThumbnailFetcher(
   thumbnail_fetcher_ = std::move(thumbnail_fetcher);
 }
 
+void PrefetchServiceTestTaco::SetThumbnailImageFetcher(
+    std::unique_ptr<image_fetcher::ImageFetcher> thumbnail_image_fetcher) {
+  CHECK(!prefetch_service_);
+  thumbnail_image_fetcher_ = std::move(thumbnail_image_fetcher);
+}
+
 void PrefetchServiceTestTaco::SetOfflinePageModel(
     std::unique_ptr<OfflinePageModel> offline_page_model) {
   CHECK(!prefetch_service_);
@@ -171,7 +182,7 @@ void PrefetchServiceTestTaco::CreatePrefetchService() {
       std::move(suggested_articles_observer_), std::move(prefetch_downloader_),
       std::move(prefetch_importer_),
       std::move(prefetch_background_task_handler_),
-      std::move(thumbnail_fetcher_));
+      std::move(thumbnail_fetcher_), std::move(thumbnail_image_fetcher_));
 }
 
 std::unique_ptr<PrefetchService>

components/offline_pages/core/prefetch/prefetch_service_test_taco.h

@@ -11,6 +11,10 @@
 #include "base/memory/ref_counted.h"
 #include "base/threading/thread_task_runner_handle.h"
 
+namespace image_fetcher {
+class ImageFetcher;
+}
+
 namespace offline_pages {
 class OfflineMetricsCollector;
 class OfflinePageModel;
@@ -71,6 +75,9 @@ class PrefetchServiceTestTaco {
           prefetch_background_task_handler);
   // Default type: MockThumbnailFetcher.
   void SetThumbnailFetcher(std::unique_ptr<ThumbnailFetcher> thumbnail_fetcher);
+  // Default type: image_fetcher::MockImageFetcher.
+  void SetThumbnailImageFetcher(
+      std::unique_ptr<image_fetcher::ImageFetcher> thumbnail_image_fetcher);
   void SetOfflinePageModel(
       std::unique_ptr<OfflinePageModel> offline_page_model);
 
@@ -104,6 +111,7 @@ class PrefetchServiceTestTaco {
       prefetch_background_task_handler_;
   std::unique_ptr<PrefetchService> prefetch_service_;
   std::unique_ptr<ThumbnailFetcher> thumbnail_fetcher_;
+  std::unique_ptr<image_fetcher::ImageFetcher> thumbnail_image_fetcher_;
   std::unique_ptr<OfflinePageModel> offline_page_model_;
   std::unique_ptr<TestDownloadService> download_service_;
   std::unique_ptr<TestDownloadClient> download_client_;

components/offline_pages/core/prefetch/prefetch_types.cc

@@ -135,6 +135,15 @@ RenderPageInfo::RenderPageInfo() = default;
 
 RenderPageInfo::RenderPageInfo(const RenderPageInfo& other) = default;
 
+PrefetchURL::PrefetchURL(const std::string& id,
+                         const GURL& url,
+                         const base::string16& title)
+    : id(id), url(url), title(title) {}
+
+PrefetchURL::~PrefetchURL() = default;
+
+PrefetchURL::PrefetchURL(const PrefetchURL& other) = default;
+
 PrefetchDownloadResult::PrefetchDownloadResult() = default;
 
 PrefetchDownloadResult::PrefetchDownloadResult(const std::string& download_id,

components/offline_pages/core/prefetch/prefetch_types.h

@@ -213,8 +213,9 @@ using PrefetchRequestFinishedCallback =
 struct PrefetchURL {
   PrefetchURL(const std::string& id,
               const GURL& url,
-              const base::string16& title)
-      : id(id), url(url), title(title) {}
+              const base::string16& title);
+  ~PrefetchURL();
+  PrefetchURL(const PrefetchURL& other);
 
   // Client provided ID to allow the matching of provided URLs to the respective
   // work item in the prefetching system within that client's assigned
@@ -227,6 +228,10 @@ struct PrefetchURL {
 
   // The title of the page.
   base::string16 title;
+
+  // URL for a thumbnail that represents the page. May be empty if no thumbnail
+  // is available.
+  GURL thumbnail_url;
 };
 
 // Result of a completed download.

components/offline_pages/core/prefetch/stub_prefetch_service.cc

@@ -64,6 +64,10 @@ OfflinePageModel* StubPrefetchService::GetOfflinePageModel() {
   return nullptr;
 }
 
+image_fetcher::ImageFetcher* StubPrefetchService::GetThumbnailImageFetcher() {
+  return nullptr;
+}
+
 SuggestedArticlesObserver*
 StubPrefetchService::GetSuggestedArticlesObserverForTesting() {
   return nullptr;

components/offline_pages/core/prefetch/stub_prefetch_service.h

@@ -29,6 +29,7 @@ class StubPrefetchService : public PrefetchService {
   PrefetchBackgroundTaskHandler* GetPrefetchBackgroundTaskHandler() override;
   ThumbnailFetcher* GetThumbnailFetcher() override;
   OfflinePageModel* GetOfflinePageModel() override;
+  image_fetcher::ImageFetcher* GetThumbnailImageFetcher() override;
 
   SuggestedArticlesObserver* GetSuggestedArticlesObserverForTesting() override;
 };

components/offline_pages/core/prefetch/tasks/add_unique_urls_task.cc

@@ -55,9 +55,9 @@ bool CreatePrefetchItemSync(sql::Database* db,
   static const char kSql[] =
       "INSERT INTO prefetch_items"
       " (offline_id, requested_url, client_namespace, client_id, creation_time,"
-      " freshness_time, title)"
+      " freshness_time, title, thumbnail_url)"
       " VALUES"
-      " (?, ?, ?, ?, ?, ?, ?)";
+      " (?, ?, ?, ?, ?, ?, ?, ?)";
 
   sql::Statement statement(db->GetCachedStatement(SQL_FROM_HERE, kSql));
   statement.BindInt64(0, store_utils::GenerateOfflineId());
@@ -67,6 +67,7 @@ bool CreatePrefetchItemSync(sql::Database* db,
   statement.BindInt64(4, now_db_time);
   statement.BindInt64(5, now_db_time);
   statement.BindString16(6, prefetch_url.title);
+  statement.BindString(7, prefetch_url.thumbnail_url.spec());
 
   return statement.Run();
 }

components/offline_pages/core/prefetch/tasks/add_unique_urls_task_unittest.cc

@@ -32,6 +32,7 @@ const char kClientId3[] = "ID-3";
 const GURL kTestURL1("https://www.google.com/");
 const GURL kTestURL2("http://www.example.com/");
 const GURL kTestURL3("https://news.google.com/");
+const char kTestThumbnailURL[] = "http://thumbnail.com/";
 const base::string16 kTestTitle1 = base::ASCIIToUTF16("Title 1");
 const base::string16 kTestTitle2 = base::ASCIIToUTF16("Title 2");
 const base::string16 kTestTitle3 = base::ASCIIToUTF16("Title 3");
@@ -69,8 +70,10 @@ TEST_F(AddUniqueUrlsTaskTest, StoreFailure) {
 
 TEST_F(AddUniqueUrlsTaskTest, AddTaskInEmptyStore) {
   std::vector<PrefetchURL> urls;
-  urls.push_back(PrefetchURL{kClientId1, kTestURL1, kTestTitle1});
-  urls.push_back(PrefetchURL{kClientId2, kTestURL2, kTestTitle2});
+  PrefetchURL url1{kClientId1, kTestURL1, kTestTitle1};
+  url1.thumbnail_url = GURL(kTestThumbnailURL);
+  urls.push_back(url1);
+  urls.emplace_back(kClientId2, kTestURL2, kTestTitle2);
   RunTask(std::make_unique<AddUniqueUrlsTask>(dispatcher(), store(),
                                               kTestNamespace, urls));
 
@@ -81,6 +84,8 @@ TEST_F(AddUniqueUrlsTaskTest, AddTaskInEmptyStore) {
   EXPECT_EQ(kTestNamespace, items[kClientId1].client_id.name_space);
   EXPECT_EQ(kTestTitle1, items[kClientId1].title);
   ASSERT_GT(items.count(kClientId2), 0U);
+  EXPECT_EQ(kTestThumbnailURL, items[kClientId1].thumbnail_url);
+  ASSERT_GT(items.count(kClientId2), 0ul);
   EXPECT_EQ(kTestURL2, items[kClientId2].url);
   EXPECT_EQ(kTestNamespace, items[kClientId2].client_id.name_space);
   EXPECT_EQ(kTestTitle2, items[kClientId2].title);

components/offline_pages/core/prefetch/tasks/get_thumbnail_info_task.cc

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/offline_pages/core/prefetch/tasks/get_thumbnail_info_task.h"
+
+#include <utility>
+
+#include "components/offline_pages/core/prefetch/store/prefetch_store.h"
+#include "sql/database.h"
+#include "sql/statement.h"
+
+namespace offline_pages {
+namespace {
+
+GetThumbnailInfoTask::Result GetThumbnailInfoSync(const int64_t offline_id,
+                                                  sql::Database* db) {
+  static const char kSql[] = R"(SELECT thumbnail_url FROM prefetch_items
+    WHERE offline_id=?;)";
+
+  sql::Statement statement(db->GetCachedStatement(SQL_FROM_HERE, kSql));
+  DCHECK(statement.is_valid());
+
+  GetThumbnailInfoTask::Result result;
+  statement.BindInt64(0, offline_id);
+  if (statement.Step())
+    result.thumbnail_url = GURL(statement.ColumnString(0));
+
+  return result;
+}
+
+}  // namespace
+
+GetThumbnailInfoTask::GetThumbnailInfoTask(PrefetchStore* store,
+                                           const int64_t offline_id,
+                                           ResultCallback callback)
+    : prefetch_store_(store),
+      offline_id_(offline_id),
+      callback_(std::move(callback)) {}
+
+GetThumbnailInfoTask::~GetThumbnailInfoTask() = default;
+
+void GetThumbnailInfoTask::Run() {
+  prefetch_store_->Execute(
+      base::BindOnce(GetThumbnailInfoSync, offline_id_),
+      base::BindOnce(&GetThumbnailInfoTask::CompleteTaskAndForwardResult,
+                     weak_factory_.GetWeakPtr()),
+      Result());
+}
+
+void GetThumbnailInfoTask::CompleteTaskAndForwardResult(Result result) {
+  TaskComplete();
+  std::move(callback_).Run(result);
+}
+
+}  // namespace offline_pages

components/offline_pages/core/prefetch/tasks/get_thumbnail_info_task.h

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_TASKS_GET_THUMBNAIL_INFO_TASK_H_
+#define COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_TASKS_GET_THUMBNAIL_INFO_TASK_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/memory/weak_ptr.h"
+#include "components/offline_pages/task/task.h"
+#include "url/gurl.h"
+
+namespace offline_pages {
+class PrefetchStore;
+
+// Task that attempts to get thumbnail information about an offline item in the
+// prefetch store.
+class GetThumbnailInfoTask : public Task {
+ public:
+  struct Result {
+    // The thumbnail URL of the offline item. This is empty if the offline item
+    // was not found, or if the item had no thumbnail URL.
+    GURL thumbnail_url;
+  };
+  using ResultCallback = base::OnceCallback<void(Result)>;
+
+  GetThumbnailInfoTask(PrefetchStore* store,
+                       const int64_t offline_id,
+                       ResultCallback callback);
+  ~GetThumbnailInfoTask() override;
+
+  // Task implementation.
+  void Run() override;
+
+ private:
+  void CompleteTaskAndForwardResult(Result result);
+  PrefetchStore* prefetch_store_;
+  int64_t offline_id_;
+  ResultCallback callback_;
+
+  base::WeakPtrFactory<GetThumbnailInfoTask> weak_factory_{this};
+
+  DISALLOW_COPY_AND_ASSIGN(GetThumbnailInfoTask);
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_TASKS_GET_THUMBNAIL_INFO_TASK_H_

components/offline_pages/core/prefetch/tasks/get_thumbnail_info_task_unittest.cc

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/offline_pages/core/prefetch/tasks/get_thumbnail_info_task.h"
+
+#include "base/test/mock_callback.h"
+#include "components/offline_pages/core/prefetch/tasks/prefetch_task_test_base.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace offline_pages {
+namespace {
+const char kTestUrl[] = "https://www.test_thumbnail.com/";
+
+class GetThumbnailInfoTaskTest : public PrefetchTaskTestBase {
+ public:
+  GetThumbnailInfoTaskTest() = default;
+  ~GetThumbnailInfoTaskTest() override = default;
+
+  PrefetchItem TestItem() {
+    PrefetchItem item =
+        item_generator()->CreateItem(PrefetchItemState::DOWNLOADED);
+    item.thumbnail_url = GURL(kTestUrl);
+    return item;
+  }
+};
+
+MATCHER(IsNullResult, "") {
+  return arg.thumbnail_url.is_empty();
+}
+
+MATCHER(IsTestUrl, "") {
+  return arg.thumbnail_url.possibly_invalid_spec() == kTestUrl;
+}
+
+TEST_F(GetThumbnailInfoTaskTest, NotPresent) {
+  const PrefetchItem item = TestItem();
+  store_util()->InsertPrefetchItem(item);
+
+  base::MockCallback<GetThumbnailInfoTask::ResultCallback> callback;
+  EXPECT_CALL(callback, Run(IsNullResult()));
+  RunTask(std::make_unique<GetThumbnailInfoTask>(store(), item.offline_id + 1,
+                                                 callback.Get()));
+}
+
+TEST_F(GetThumbnailInfoTaskTest, Found) {
+  const PrefetchItem item = TestItem();
+  store_util()->InsertPrefetchItem(item);
+
+  base::MockCallback<GetThumbnailInfoTask::ResultCallback> callback;
+  EXPECT_CALL(callback, Run(IsTestUrl()));
+  RunTask(std::make_unique<GetThumbnailInfoTask>(store(), item.offline_id,
+                                                 callback.Get()));
+}
+
+}  // namespace
+}  // namespace offline_pages

components/offline_pages/core/prefetch/thumbnail_fetch_by_url.cc

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/offline_pages/core/prefetch/thumbnail_fetch_by_url.h"
+
+#include <utility>
+
+#include "base/bind.h"
+#include "components/image_fetcher/core/image_fetcher.h"
+
+namespace offline_pages {
+
+namespace {
+net::NetworkTrafficAnnotationTag TrafficAnnotation() {
+  return net::DefineNetworkTrafficAnnotation("prefetch_thumbnail", R"(
+        semantics {
+          sender: "Offline Pages Prefetch"
+          description:
+            "Chromium fetches suggested articles for offline viewing. This"
+            " network request is for a thumbnail that matches the article."
+          trigger:
+            "Two attempts, directly before and after the article is fetched."
+          data:
+            "The requested thumbnail URL."
+          destination: GOOGLE_OWNED_SERVICE
+        }
+        policy {
+          cookies_allowed: NO
+          setting:
+            "Users can enable or disable offline prefetch by toggling "
+            "'Download articles for you' in settings under Downloads or "
+            "by toggling chrome://flags#offline-prefetch."
+          chrome_policy {
+            NTPContentSuggestionsEnabled {
+              policy_options {mode: MANDATORY}
+              NTPContentSuggestionsEnabled: false
+            }
+          }
+        })");
+}
+
+}  // namespace
+
+void FetchThumbnailByURL(
+    base::OnceCallback<void(const std::string& image_data)> callback,
+    image_fetcher::ImageFetcher* fetcher,
+    const GURL thumbnail_url) {
+  auto forward_callback =
+      [](base::OnceCallback<void(const std::string& image_data)> callback,
+         const std::string& image_data,
+         const image_fetcher::RequestMetadata& request_metadata) {
+        std::move(callback).Run(image_data);
+      };
+  fetcher->FetchImageData(/*id=*/std::string(), thumbnail_url,
+                          base::BindOnce(forward_callback, std::move(callback)),
+                          TrafficAnnotation());
+}
+
+}  // namespace offline_pages

components/offline_pages/core/prefetch/thumbnail_fetch_by_url.h

+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_THUMBNAIL_FETCH_BY_URL_H_
+#define COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_THUMBNAIL_FETCH_BY_URL_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "url/gurl.h"
+
+namespace image_fetcher {
+class ImageFetcher;
+}  // namespace image_fetcher
+
+namespace offline_pages {
+
+// Attempts to fetch a thumbnail, and returns the result to callback.
+// |image_data| will be empty if the thumbnail fetch fails. Otherwise,
+// |image_data| contains the raw image data (typically JPEG).
+void FetchThumbnailByURL(
+    base::OnceCallback<void(const std::string& image_data)> callback,
+    image_fetcher::ImageFetcher* fetcher,
+    const GURL thumbnail_url);
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_CORE_PREFETCH_THUMBNAIL_FETCH_BY_URL_H_

tools/traffic_annotation/summary/annotations.xml

@@ -163,7 +163,7 @@ Refer to README.md for content description and update process.
  <item id="oauth2_api_call_flow" hash_code="29188932" type="2" content_hash_code="108831236" os_list="linux,windows" policy_fields="-1" file_path="google_apis/gaia/oauth2_api_call_flow.cc"/>
  <item id="oauth2_mint_token_flow" hash_code="1112842" type="1" second_id="29188932" content_hash_code="91581432" os_list="linux,windows" semantics_fields="1,2,3,4,5" policy_fields="3,4" file_path="google_apis/gaia/oauth2_mint_token_flow.cc"/>
  <item id="ocsp_start_url_request" hash_code="60921996" type="0" content_hash_code="24127780" os_list="linux" file_path="net/cert_net/nss_ocsp.cc"/>
- <item id="offline_prefetch" hash_code="19185953" type="0" content_hash_code="57248156" os_list="linux,windows" file_path="components/offline_pages/core/prefetch/prefetch_request_fetcher.cc"/>
+ <item id="offline_prefetch" hash_code="19185953" type="0" content_hash_code="112039446" os_list="linux,windows" file_path="components/offline_pages/core/prefetch/prefetch_request_fetcher.cc"/>
  <item id="omnibox_documentsuggest" hash_code="6055066" type="0" content_hash_code="126973249" os_list="linux,windows" file_path="components/omnibox/browser/document_suggestions_service.cc"/>
  <item id="omnibox_navigation_observer" hash_code="61684939" type="0" content_hash_code="70941231" os_list="linux,windows" file_path="chrome/browser/ui/omnibox/chrome_omnibox_navigation_observer.cc"/>
  <item id="omnibox_prefetch_image" hash_code="109200878" type="0" content_hash_code="107906693" os_list="linux,windows" file_path="chrome/browser/autocomplete/chrome_autocomplete_provider_client.cc"/>
@@ -194,7 +194,8 @@ Refer to README.md for content description and update process.
  <item id="popular_sites_fetch" hash_code="50755044" type="0" content_hash_code="6910083" os_list="linux,windows" file_path="components/ntp_tiles/popular_sites_impl.cc"/>
  <item id="port_forwarding_controller_socket" hash_code="95075845" type="0" content_hash_code="122163428" os_list="linux,windows" file_path="chrome/browser/devtools/device/port_forwarding_controller.cc"/>
  <item id="ppapi_download_request" hash_code="135967426" type="0" content_hash_code="110461402" os_list="linux,windows" file_path="chrome/browser/safe_browsing/download_protection/ppapi_download_request.cc"/>
- <item id="prefetch_download" hash_code="44583172" type="0" content_hash_code="100587691" os_list="linux,windows" file_path="components/offline_pages/core/prefetch/prefetch_downloader_impl.cc"/>
+ <item id="prefetch_download" hash_code="44583172" type="0" content_hash_code="21424542" os_list="linux,windows" file_path="components/offline_pages/core/prefetch/prefetch_downloader_impl.cc"/>
+ <item id="prefetch_thumbnail" hash_code="83519268" type="0" content_hash_code="6947363" os_list="linux,windows" file_path="components/offline_pages/core/prefetch/thumbnail_fetch_by_url.cc"/>
  <item id="printer_job_handler" hash_code="67638271" type="1" second_id="111712433" content_hash_code="75712693" os_list="linux,windows" semantics_fields="2,3,4" file_path="chrome/service/cloud_print/printer_job_handler.cc"/>
  <item id="privet_http_impl" hash_code="71251498" type="0" content_hash_code="107348604" os_list="linux,windows" file_path="chrome/browser/printing/cloud_print/privet_http_impl.cc"/>
  <item id="profile_avatar" hash_code="51164680" type="0" content_hash_code="113550845" os_list="linux,windows" file_path="chrome/browser/profiles/profile_avatar_downloader.cc"/>