Integrate Lite Page Server Previews with the Previews Stack

Adds Lite Page Server Previews to DetermineAllowedPreviews and
DetermineCommitted. For now, the preview is always allowed if the
feature is enabled and is committed if the URL matches.

This intentionally leaves an open question about whether more logic
in the NavigationThrottle can/should be moved into the DeciderImpl.

The biggest part of this change is moving the URL checking logic to
the previews component and adding additional helper functions there.

Bug: 898557
Change-Id: Iccc0b672eeedbe23942f4d17f6afd214426372a9
Reviewed-on: https://chromium-review.googlesource.com/c/1323800
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Doug Arnett <dougarnett@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607427}

chrome/browser/chrome_content_browser_client.cc

@@ -5126,13 +5126,6 @@ ChromeContentBrowserClient::DetermineCommittedPreviewsForURL(
       data_reduction_proxy::ContentLoFiDecider::
           DetermineCommittedServerPreviewsState(drp_data, initial_state);
 
-  // Check if the current URL indicates that we redirected to HTTPS server
-  // previews.
-  if (PreviewsLitePageNavigationThrottle::GetOriginalURL(
-          url, nullptr /* original_url */)) {
-    return previews_state & content::LITE_PAGE_REDIRECT_ON;
-  }
-
   // Check the various other client previews types.
   return previews::DetermineCommittedClientPreviewsState(
       previews_user_data, url, previews_state, previews_decider);

chrome/browser/previews/android/previews_android_bridge.cc

@@ -7,10 +7,10 @@
 #include <memory>
 
 #include "base/android/jni_android.h"
-#include "chrome/browser/previews/previews_lite_page_navigation_throttle.h"
 #include "chrome/browser/previews/previews_ui_tab_helper.h"
 #include "components/previews/content/previews_user_data.h"
 #include "components/previews/core/previews_experiments.h"
+#include "components/previews/core/previews_lite_page_url_handler.h"
 #include "content/public/browser/web_contents.h"
 #include "jni/PreviewsAndroidBridge_jni.h"
 
@@ -56,8 +56,8 @@ PreviewsAndroidBridge::GetLitePageRedirectOriginalURL(
     const base::android::JavaParamRef<jstring>& j_visible_url) {
   GURL visible_url(base::android::ConvertJavaStringToUTF16(env, j_visible_url));
   std::string original_url;
-  if (PreviewsLitePageNavigationThrottle::GetOriginalURL(visible_url,
-                                                         &original_url)) {
+  if (previews::ExtractOriginalURLFromLitePageRedirectURL(visible_url,
+                                                          &original_url)) {
     return base::android::ScopedJavaLocalRef<jstring>(
         base::android::ConvertUTF8ToJavaString(env, original_url));
   }

chrome/browser/previews/previews_lite_page_browsertest.cc

@@ -26,17 +26,23 @@
 #include "chrome/browser/previews/previews_lite_page_navigation_throttle.h"
 #include "chrome/browser/previews/previews_service.h"
 #include "chrome/browser/previews/previews_service_factory.h"
+#include "chrome/browser/previews/previews_ui_tab_helper.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
+#include "chrome/grit/generated_resources.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client_test_utils.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_service.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.h"
 #include "components/data_reduction_proxy/proto/data_store.pb.h"
+#include "components/infobars/core/confirm_infobar_delegate.h"
 #include "components/infobars/core/infobar.h"
 #include "components/prefs/pref_service.h"
+#include "components/previews/content/previews_user_data.h"
+#include "components/previews/core/previews_experiments.h"
 #include "components/previews/core/previews_features.h"
+#include "components/previews/core/previews_lite_page_url_handler.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/page_type.h"
@@ -47,6 +53,7 @@
 #include "net/test/embedded_test_server/http_request.h"
 #include "net/test/embedded_test_server/http_response.h"
 #include "services/network/test/test_network_quality_tracker.h"
+#include "ui/base/l10n/l10n_util.h"
 #include "url/gurl.h"
 
 class PreviewsLitePageServerBrowserTest : public InProcessBrowserTest {
@@ -224,6 +231,17 @@ class PreviewsLitePageServerBrowserTest : public InProcessBrowserTest {
     // this validation to flake. Waiting for the load stop on the page will
     // ensure that the Virtual URL has been set.
     content::WaitForLoadStop(GetWebContents());
+    base::RunLoop().RunUntilIdle();
+
+    PreviewsUITabHelper* ui_tab_helper =
+        PreviewsUITabHelper::FromWebContents(GetWebContents());
+    EXPECT_TRUE(ui_tab_helper->displayed_preview_ui());
+
+    previews::PreviewsUserData* previews_data =
+        ui_tab_helper->previews_user_data();
+    EXPECT_TRUE(previews_data->HasCommittedPreviewsType());
+    EXPECT_EQ(previews_data->committed_previews_type(),
+              previews::PreviewsType::LITE_PAGE_REDIRECT);
 
     const GURL loaded_url = GetLoadedURL();
     const GURL previews_host = previews_server();
@@ -255,6 +273,17 @@ class PreviewsLitePageServerBrowserTest : public InProcessBrowserTest {
     // this validation to flake. Waiting for the load stop on the page will
     // ensure that the Virtual URL has been set.
     content::WaitForLoadStop(GetWebContents());
+    base::RunLoop().RunUntilIdle();
+
+    PreviewsUITabHelper* ui_tab_helper =
+        PreviewsUITabHelper::FromWebContents(GetWebContents());
+    EXPECT_FALSE(ui_tab_helper->displayed_preview_ui());
+
+    previews::PreviewsUserData* previews_data =
+        ui_tab_helper->previews_user_data();
+    EXPECT_FALSE(previews_data->HasCommittedPreviewsType());
+    EXPECT_NE(previews_data->committed_previews_type(),
+              previews::PreviewsType::LITE_PAGE_REDIRECT);
 
     const GURL loaded_url = GetLoadedURL();
     const GURL previews_host = previews_server();
@@ -412,7 +441,7 @@ class PreviewsLitePageServerBrowserTest : public InProcessBrowserTest {
     std::string original_url_str;
 
     // Ignore anything that's not a previews request with an unused status.
-    if (!PreviewsLitePageNavigationThrottle::GetOriginalURL(
+    if (!previews::ExtractOriginalURLFromLitePageRedirectURL(
             request.GetURL(), &original_url_str)) {
       response->set_code(net::HttpStatusCode::HTTP_BAD_REQUEST);
       return response;
@@ -1079,13 +1108,22 @@ IN_PROC_BROWSER_TEST_F(
 
   VerifyPreviewNotLoaded();
   ClearDeciderState();
-  EXPECT_EQ(1U, GetInfoBarService()->infobar_count());
+  ASSERT_EQ(1U, GetInfoBarService()->infobar_count());
+  EXPECT_EQ(l10n_util::GetStringUTF16(IDS_LITE_PAGE_PREVIEWS_MESSAGE),
+            static_cast<ConfirmInfoBarDelegate*>(
+                GetInfoBarService()->infobar_at(0)->delegate())
+                ->GetMessageText());
   histogram_tester.ExpectBucketCount(
       "Previews.ServerLitePage.IneligibleReasons",
       PreviewsLitePageNavigationThrottle::IneligibleReason::kInfoBarNotSeen, 1);
 
   ui_test_utils::NavigateToURL(browser(), HttpsLitePageURL(kSuccess));
-  EXPECT_EQ(0U, GetInfoBarService()->infobar_count());
+  // Expect the "Saved Data" InfoBar.
+  ASSERT_EQ(1U, GetInfoBarService()->infobar_count());
+  EXPECT_EQ(l10n_util::GetStringUTF16(IDS_PREVIEWS_INFOBAR_SAVED_DATA_TITLE),
+            static_cast<ConfirmInfoBarDelegate*>(
+                GetInfoBarService()->infobar_at(0)->delegate())
+                ->GetMessageText());
   VerifyPreviewLoaded();
 }
 

chrome/browser/previews/previews_lite_page_decider.cc

@@ -188,7 +188,7 @@ PreviewsLitePageDecider::MaybeCreateThrottleFor(
       previews_service->previews_lite_page_decider();
   DCHECK(decider);
 
-  // TODO(crbug/842233): Replace this logic with PreviewsState.
+  // TODO(crbug/898557): Replace this logic with PreviewsState.
   bool drp_enabled = decider->drp_settings_->IsDataReductionProxyEnabled();
   bool preview_enabled = previews::params::ArePreviewsAllowed() &&
                          previews::params::IsLitePageServerPreviewsEnabled();

chrome/browser/previews/previews_lite_page_navigation_throttle.cc

@@ -25,6 +25,7 @@
 #include "components/base32/base32.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
 #include "components/previews/core/previews_experiments.h"
+#include "components/previews/core/previews_lite_page_url_handler.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_task_traits.h"
 #include "content/public/browser/browser_thread.h"
@@ -51,12 +52,6 @@ constexpr char kChromeProxyHeader[] = "chrome-proxy";
 
 const base::TimeDelta kBlacklistDuration = base::TimeDelta::FromDays(30);
 
-bool IsPreviewsDomain(const GURL& url) {
-  GURL previews_host = previews::params::GetLitePagePreviewsDomainURL();
-  return url.DomainIs(previews_host.host()) &&
-         url.EffectiveIntPort() == previews_host.EffectiveIntPort();
-}
-
 bool IsPrivateDomain(const GURL& url) {
   if (url.host().find(".") == base::StringPiece::npos)
     return true;
@@ -160,14 +155,15 @@ bool HandlePreviewsLitePageURLRewrite(
     content::BrowserContext* browser_context) {
   // Don't change the |url|, just register our interest in reversing it before
   // it is displayed to the user in |HandlePreviewsLitePageURLRewriteReverse|.
-  return !!PreviewsLitePageNavigationThrottle::GetOriginalURL(*url, nullptr);
+  return previews::IsLitePageRedirectPreviewURL(*url);
 }
 
 bool HandlePreviewsLitePageURLRewriteReverse(
     GURL* url,
     content::BrowserContext* browser_context) {
   std::string original_url;
-  if (PreviewsLitePageNavigationThrottle::GetOriginalURL(*url, &original_url)) {
+  if (previews::ExtractOriginalURLFromLitePageRedirectURL(*url,
+                                                          &original_url)) {
     *url = GURL(original_url);
     return true;
   }
@@ -221,7 +217,7 @@ bool PreviewsLitePageNavigationThrottle::IsEligibleForPreview() const {
   // Check dynamic blacklists.
   std::vector<BlacklistReason> blacklist_reasons;
 
-  if (IsPreviewsDomain(url))
+  if (previews::IsLitePageRedirectPreviewDomain(url))
     blacklist_reasons.push_back(BlacklistReason::kNavigationToPreviewsDomain);
 
   if (IsPrivateDomain(url))
@@ -258,25 +254,6 @@ bool PreviewsLitePageNavigationThrottle::IsEligibleForPreview() const {
   return true;
 }
 
-// static
-bool PreviewsLitePageNavigationThrottle::GetOriginalURL(
-    const GURL& url,
-    std::string* original_url) {
-  if (!url.is_valid())
-    return false;
-
-  if (!IsPreviewsDomain(url))
-    return false;
-
-  std::string original_url_query_param;
-  if (!net::GetValueForKeyInQuery(url, "u", &original_url_query_param))
-    return false;
-
-  if (original_url)
-    *original_url = original_url_query_param;
-  return true;
-}
-
 // static
 GURL PreviewsLitePageNavigationThrottle::GetPreviewsURLForURL(
     const GURL& original_url) {
@@ -307,7 +284,8 @@ GURL PreviewsLitePageNavigationThrottle::GetPreviewsURLForURL(
 }
 
 GURL PreviewsLitePageNavigationThrottle::GetPreviewsURL() const {
-  DCHECK(!IsPreviewsDomain(navigation_handle()->GetURL()));
+  DCHECK(!previews::IsLitePageRedirectPreviewDomain(
+      navigation_handle()->GetURL()));
   return GetPreviewsURLForURL(navigation_handle()->GetURL());
 }
 
@@ -417,7 +395,8 @@ PreviewsLitePageNavigationThrottle::MaybeNavigateToPreview() const {
   std::string original_url;
   if (navigation_handle()->GetReloadType() ==
           content::ReloadType::ORIGINAL_REQUEST_URL &&
-      GetOriginalURL(navigation_handle()->GetURL(), &original_url)) {
+      previews::ExtractOriginalURLFromLitePageRedirectURL(
+          navigation_handle()->GetURL(), &original_url)) {
     LoadAndBypass(navigation_handle()->GetWebContents(), manager_,
                   MakeOpenURLParams(navigation_handle(), GURL(original_url),
                                     std::string()),
@@ -455,7 +434,8 @@ PreviewsLitePageNavigationThrottle::WillRedirectRequest() {
 
   // If we are redirecting on a preview, count some UMA and proceed.
   std::string original_url;
-  if (GetOriginalURL(previous_url, &original_url)) {
+  if (previews::ExtractOriginalURLFromLitePageRedirectURL(previous_url,
+                                                          &original_url)) {
     // A redirect means one of two things: (1) there is no preview available for
     // this page and we should redirect back to the original page. (2) the
     // previews server is forwarding along a redirect from the origin. The
@@ -501,8 +481,10 @@ PreviewsLitePageNavigationThrottle::WillRedirectRequest() {
 content::NavigationThrottle::ThrottleCheckResult
 PreviewsLitePageNavigationThrottle::WillFailRequest() {
   std::string original_url;
-  if (!GetOriginalURL(navigation_handle()->GetURL(), &original_url))
+  if (!previews::ExtractOriginalURLFromLitePageRedirectURL(
+          navigation_handle()->GetURL(), &original_url)) {
     return content::NavigationThrottle::PROCEED;
+  }
 
   UMA_HISTOGRAM_ENUMERATION("Previews.ServerLitePage.ServerResponse",
                             ServerResponse::kFailed);
@@ -520,7 +502,8 @@ PreviewsLitePageNavigationThrottle::WillFailRequest() {
 content::NavigationThrottle::ThrottleCheckResult
 PreviewsLitePageNavigationThrottle::WillProcessResponse() {
   std::string original_url;
-  if (!GetOriginalURL(navigation_handle()->GetURL(), &original_url)) {
+  if (!previews::ExtractOriginalURLFromLitePageRedirectURL(
+          navigation_handle()->GetURL(), &original_url)) {
     // Return early if this request was not for a Preview.
     return content::NavigationThrottle::PROCEED;
   }

chrome/browser/previews/previews_lite_page_navigation_throttle.h

@@ -99,11 +99,6 @@ class PreviewsLitePageNavigationThrottle : public content::NavigationThrottle {
 
   ~PreviewsLitePageNavigationThrottle() override;
 
-  // Attempts to extract the original URL from the given Previews URL. Returns
-  // false if |url| is not a valid Preview URL. It is ok to pass nullptr for
-  // |original_url| if you only want the boolean return value.
-  static bool GetOriginalURL(const GURL& url, std::string* original_url);
-
   // Returns the URL for a preview given by the url.
   static GURL GetPreviewsURLForURL(const GURL& original_url);
 

chrome/browser/previews/previews_lite_page_navigation_throttle_unittest.cc

@@ -100,44 +100,3 @@ TEST(PreviewsLitePageNavigationThrottleTest, TestGetPreviewsURL) {
               GURL(test_case.previews_url));
   }
 }
-
-TEST(PreviewsLitePageNavigationThrottleTest, TestGetOriginalURL) {
-  struct TestCase {
-    std::string previews_host;
-    std::string original_url;
-    std::string previews_url;
-    bool want_ok;
-  };
-  const TestCase kTestCases[]{
-      // Use https://play.golang.org/p/HUM2HxmUTOW to compute |previews_url|.
-      {
-          "https://previews.host.com",
-          "https://original.host.com/path/path/path?query=yes",
-          "https://shta44dh4bi7rc6fnpjnkrtytwlabygjhk53v2trlot2wddylwua."
-          "previews.host.com/p?u="
-          "https%3A%2F%2Foriginal.host.com%2Fpath%2Fpath%2Fpath%3Fquery%3Dyes",
-          true,
-      },
-      {
-          "https://previews.host.com",
-          "http://original.host.com/path/path/path?query=yes",
-          "https://6p7dar4ju6r4ynz7x3pucmlcltuqsf7z5auhvckzln7voglkt56q."
-          "previews.host.com/p?u="
-          "http%3A%2F%2Foriginal.host.com%2Fpath%2Fpath%2Fpath%3Fquery%3Dyes",
-          true,
-      },
-  };
-
-  for (const TestCase& test_case : kTestCases) {
-    base::test::ScopedFeatureList scoped_feature_list;
-    scoped_feature_list.InitAndEnableFeatureWithParameters(
-        previews::features::kLitePageServerPreviews,
-        {{"previews_host", test_case.previews_host}});
-
-    std::string original_url;
-    bool got_ok = PreviewsLitePageNavigationThrottle::GetOriginalURL(
-        GURL(test_case.previews_url), &original_url);
-    EXPECT_EQ(got_ok, test_case.want_ok);
-    EXPECT_EQ(original_url, test_case.original_url);
-  }
-}

chrome/browser/previews/previews_ui_tab_helper.cc

@@ -123,6 +123,7 @@ void PreviewsUITabHelper::ShowUIElement(
 
 #if defined(OS_ANDROID)
   if (previews::params::IsPreviewsOmniboxUiEnabled()) {
+    displayed_preview_ui_ = true;
     should_display_android_omnibox_badge_ = true;
     return;
   }

chrome/browser/previews/previews_ui_tab_helper_unittest.cc

@@ -174,7 +174,7 @@ TEST_F(PreviewsUITabHelperUnitTest, DidFinishNavigationDisplaysOmniboxBadge) {
   base::RunLoop().RunUntilIdle();
 
   EXPECT_TRUE(ui_tab_helper->should_display_android_omnibox_badge());
-  EXPECT_FALSE(ui_tab_helper->displayed_preview_ui());
+  EXPECT_TRUE(ui_tab_helper->displayed_preview_ui());
   EXPECT_EQ(0U, infobar_service()->infobar_count());
 }
 #endif

components/previews/content/previews_content_util.cc

@@ -6,6 +6,7 @@
 
 #include "base/metrics/histogram_macros.h"
 #include "components/previews/content/previews_user_data.h"
+#include "components/previews/core/previews_lite_page_url_handler.h"
 
 namespace previews {
 
@@ -52,6 +53,15 @@ content::PreviewsState DetermineAllowedClientPreviewsState(
   if (!is_data_saver_user)
     return previews_state;
 
+  // Check for client-side previews in precedence order.
+  // Note: this is for the beginning of navigation so we should not
+  // check for https here (since an http request may redirect to https).
+  if (previews_decider->ShouldAllowPreviewAtNavigationStart(
+          previews_data, url, is_reload,
+          previews::PreviewsType::LITE_PAGE_REDIRECT)) {
+    previews_state |= content::LITE_PAGE_REDIRECT_ON;
+  }
+
   if (previews_decider->ShouldAllowPreviewAtNavigationStart(
           previews_data, url, is_reload,
           previews::PreviewsType::RESOURCE_LOADING_HINTS)) {
@@ -60,9 +70,6 @@ content::PreviewsState DetermineAllowedClientPreviewsState(
     previews_decider->LoadResourceHints(url);
   }
 
-  // Check for client-side previews in precedence order.
-  // Note: this is for the beginning of navigation so we should not
-  // check for https here (since an http request may redirect to https).
   if (previews_decider->ShouldAllowPreviewAtNavigationStart(
           previews_data, url, is_reload, previews::PreviewsType::NOSCRIPT)) {
     previews_state |= content::NOSCRIPT_ON;
@@ -115,6 +122,14 @@ content::PreviewsState DetermineCommittedClientPreviewsState(
     return content::PREVIEWS_OFF;
   }
 
+  // Check if a LITE_PAGE_REDIRECT preview was actually served.
+  if (previews_state & content::LITE_PAGE_REDIRECT_ON) {
+    if (IsLitePageRedirectPreviewURL(url))
+      return content::LITE_PAGE_REDIRECT_ON;
+    previews_state &= ~content::LITE_PAGE_REDIRECT_ON;
+  }
+  DCHECK(!IsLitePageRedirectPreviewURL(url));
+
   // Make priority decision among allowed client preview types that can be
   // decided at Commit time.
   if (previews_state & content::RESOURCE_LOADING_HINTS_ON) {
@@ -159,6 +174,8 @@ previews::PreviewsType GetMainFramePreviewsType(
   // The order is important here.
   if (previews_state & content::OFFLINE_PAGE_ON)
     return previews::PreviewsType::OFFLINE;
+  if (previews_state & content::LITE_PAGE_REDIRECT_ON)
+    return previews::PreviewsType::LITE_PAGE_REDIRECT;
   if (previews_state & content::SERVER_LITE_PAGE_ON)
     return previews::PreviewsType::LITE_PAGE;
   if (previews_state & content::SERVER_LOFI_ON)

components/previews/content/previews_content_util_unittest.cc

@@ -226,6 +226,34 @@ TEST_F(PreviewsContentUtilTest,
                 is_data_saver_user, enabled_previews_decider()));
 }
 
+TEST_F(PreviewsContentUtilTest,
+       DetermineAllowedClientPreviewsStateLitePageRedirect) {
+  // Enable both Client LoFi and NoScript.
+  base::test::ScopedFeatureList scoped_feature_list;
+  scoped_feature_list.InitFromCommandLine("Previews,LitePageServerPreviews",
+                                          std::string());
+
+  PreviewsUserData user_data(1);
+  bool is_reload = false;
+  bool is_redirect = false;
+  bool is_data_saver_user = true;
+  // Verify preview is enabled on HTTP and HTTPS.
+  EXPECT_TRUE(content::LITE_PAGE_REDIRECT_ON &
+              previews::DetermineAllowedClientPreviewsState(
+                  &user_data, GURL("https://www.google.com"), is_reload,
+                  is_redirect, is_data_saver_user, enabled_previews_decider()));
+  EXPECT_TRUE(content::LITE_PAGE_REDIRECT_ON &
+              previews::DetermineAllowedClientPreviewsState(
+                  &user_data, GURL("http://www.google.com"), is_reload,
+                  is_redirect, is_data_saver_user, enabled_previews_decider()));
+
+  // Verify non-HTTP[S] URL has no previews enabled.
+  EXPECT_EQ(content::PREVIEWS_UNSPECIFIED,
+            previews::DetermineAllowedClientPreviewsState(
+                &user_data, GURL("data://someblob"), is_reload, is_redirect,
+                is_data_saver_user, enabled_previews_decider()));
+}
+
 TEST_F(PreviewsContentUtilTest, DetermineCommittedClientPreviewsState) {
   base::test::ScopedFeatureList scoped_feature_list;
   scoped_feature_list.InitFromCommandLine(
@@ -241,6 +269,25 @@ TEST_F(PreviewsContentUtilTest, DetermineCommittedClientPreviewsState) {
                     content::CLIENT_LOFI_ON | content::NOSCRIPT_ON,
                 enabled_previews_decider()));
 
+  content::PreviewsState lite_page_redirect_enabled =
+      content::CLIENT_LOFI_ON | content::NOSCRIPT_ON |
+      content::RESOURCE_LOADING_HINTS_ON | content::LITE_PAGE_REDIRECT_ON;
+
+  // LITE_PAGE_REDIRECT takes precedence over NoScript, Resource Loading Hints,
+  // and Client LoFi when the committed URL is for the lite page previews
+  // server.
+  EXPECT_EQ(
+      content::LITE_PAGE_REDIRECT_ON,
+      previews::DetermineCommittedClientPreviewsState(
+          &user_data, GURL("https://litepages.googlezip.net/?u=google.com"),
+          lite_page_redirect_enabled, enabled_previews_decider()));
+
+  // Verify LITE_PAGE_REDIRECT_ON not committed for non-lite-page-sever URL.
+  EXPECT_NE(content::LITE_PAGE_REDIRECT_ON,
+            previews::DetermineCommittedClientPreviewsState(
+                &user_data, GURL("https://www.google.com"),
+                lite_page_redirect_enabled, enabled_previews_decider()));
+
   // NoScript has precedence over Client LoFi - kept for committed HTTPS:
   EXPECT_EQ(content::NOSCRIPT_ON,
             previews::DetermineCommittedClientPreviewsState(
@@ -305,6 +352,8 @@ TEST_F(PreviewsContentUtilTest, GetMainFramePreviewsType) {
       previews::GetMainFramePreviewsType(content::RESOURCE_LOADING_HINTS_ON));
   EXPECT_EQ(previews::PreviewsType::LOFI,
             previews::GetMainFramePreviewsType(content::CLIENT_LOFI_ON));
+  EXPECT_EQ(previews::PreviewsType::LITE_PAGE_REDIRECT,
+            previews::GetMainFramePreviewsType(content::LITE_PAGE_REDIRECT_ON));
 
   // NONE cases:
   EXPECT_EQ(previews::PreviewsType::NONE,
@@ -331,6 +380,11 @@ TEST_F(PreviewsContentUtilTest, GetMainFramePreviewsType) {
             previews::GetMainFramePreviewsType(
                 content::NOSCRIPT_ON | content::CLIENT_LOFI_ON |
                 content::RESOURCE_LOADING_HINTS_ON));
+  EXPECT_EQ(
+      previews::PreviewsType::LITE_PAGE_REDIRECT,
+      previews::GetMainFramePreviewsType(
+          content::NOSCRIPT_ON | content::CLIENT_LOFI_ON |
+          content::RESOURCE_LOADING_HINTS_ON | content::LITE_PAGE_REDIRECT_ON));
 }
 
 }  // namespace

components/previews/core/BUILD.gn

@@ -15,6 +15,8 @@ static_library("core") {
     "previews_experiments.h",
     "previews_features.cc",
     "previews_features.h",
+    "previews_lite_page_url_handler.cc",
+    "previews_lite_page_url_handler.h",
     "previews_logger.cc",
     "previews_logger.h",
     "previews_logger_observer.h",
@@ -58,6 +60,7 @@ source_set("unit_tests") {
     "host_filter_unittest.cc",
     "previews_black_list_unittest.cc",
     "previews_experiments_unittest.cc",
+    "previews_lite_page_url_handler_unittest.cc",
     "previews_logger_unittest.cc",
   ]
 

components/previews/core/previews_lite_page_url_handler.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/previews/core/previews_lite_page_url_handler.h"
+
+#include "components/previews/core/previews_experiments.h"
+#include "net/base/url_util.h"
+
+namespace previews {
+
+bool IsLitePageRedirectPreviewDomain(const GURL& url) {
+  if (!url.is_valid())
+    return false;
+
+  GURL previews_host = params::GetLitePagePreviewsDomainURL();
+  return url.DomainIs(previews_host.host()) &&
+         url.EffectiveIntPort() == previews_host.EffectiveIntPort();
+}
+
+bool IsLitePageRedirectPreviewURL(const GURL& url) {
+  return ExtractOriginalURLFromLitePageRedirectURL(url, nullptr);
+}
+
+bool ExtractOriginalURLFromLitePageRedirectURL(const GURL& url,
+                                               std::string* original_url) {
+  if (!IsLitePageRedirectPreviewDomain(url))
+    return false;
+
+  std::string original_url_query_param;
+  if (!net::GetValueForKeyInQuery(url, "u", &original_url_query_param))
+    return false;
+
+  if (original_url)
+    *original_url = original_url_query_param;
+  return true;
+}
+
+}  // namespace previews

components/previews/core/previews_lite_page_url_handler.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_PREVIEWS_CORE_PREVIEWS_LITE_PAGE_URL_HANDLER_H_
+#define COMPONENTS_PREVIEWS_CORE_PREVIEWS_LITE_PAGE_URL_HANDLER_H_
+
+#include <string>
+
+#include "url/gurl.h"
+
+namespace previews {
+
+// Returns true if the given |url| has the same domain as the lite page previews
+// server.
+bool IsLitePageRedirectPreviewDomain(const GURL& url);
+
+// Returns true if the given URL is a Lite Page Preview URL. This does more
+// checking than |IsLitePageRedirectPreviewDomain| so be sure to use the right
+// one.
+bool IsLitePageRedirectPreviewURL(const GURL& url);
+
+// Attempts to extract the original URL from the given Previews URL. Returns
+// false if |url| is not a valid Preview URL.
+bool ExtractOriginalURLFromLitePageRedirectURL(const GURL& url,
+                                               std::string* original_url);
+
+}  // namespace previews
+
+#endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_LITE_PAGE_URL_HANDLER_H_

components/previews/core/previews_lite_page_url_handler_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/previews/core/previews_lite_page_url_handler.h"
+
+#include <memory>
+
+#include "base/test/scoped_feature_list.h"
+#include "components/previews/core/previews_features.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace previews {
+
+TEST(PreviewsLitePageURLHandlerTest,
+     TestExtractOriginalURLFromLitePageRedirectURL) {
+  struct TestCase {
+    std::string previews_host;
+    std::string original_url;
+    std::string previews_url;
+    bool want_ok;
+  };
+  const TestCase kTestCases[]{
+      // Use https://play.golang.org/p/HUM2HxmUTOW to compute |previews_url|.
+      {
+          "https://previews.host.com",
+          "https://original.host.com/path/path/path?query=yes",
+          "https://shta44dh4bi7rc6fnpjnkrtytwlabygjhk53v2trlot2wddylwua."
+          "previews.host.com/p?u="
+          "https%3A%2F%2Foriginal.host.com%2Fpath%2Fpath%2Fpath%3Fquery%3Dyes",
+          true,
+      },
+      {
+          "https://previews.host.com",
+          "http://original.host.com/path/path/path?query=yes",
+          "https://6p7dar4ju6r4ynz7x3pucmlcltuqsf7z5auhvckzln7voglkt56q."
+          "previews.host.com/p?u="
+          "http%3A%2F%2Foriginal.host.com%2Fpath%2Fpath%2Fpath%3Fquery%3Dyes",
+          true,
+      },
+  };
+
+  for (const TestCase& test_case : kTestCases) {
+    base::test::ScopedFeatureList scoped_feature_list;
+    scoped_feature_list.InitAndEnableFeatureWithParameters(
+        features::kLitePageServerPreviews,
+        {{"previews_host", test_case.previews_host}});
+
+    std::string original_url;
+    bool got_ok = ExtractOriginalURLFromLitePageRedirectURL(
+        GURL(test_case.previews_url), &original_url);
+    EXPECT_EQ(got_ok, test_case.want_ok);
+    EXPECT_EQ(original_url, test_case.original_url);
+  }
+}
+
+}  // namespace previews