Adding data savings reporting to Previews URLLoader

This CL adds reporting Data savings based on original content length
header vs content length header in the HTTPS Server previews URLLoader
implementation.

Bug: 921757
Change-Id: I38ac67b43b3fd1bc17f27a4ec7e0a8a65229cc81
Reviewed-on: https://chromium-review.googlesource.com/c/1488062
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635736}

chrome/browser/previews/previews_lite_page_browsertest.cc

@@ -1258,8 +1258,6 @@ IN_PROC_BROWSER_TEST_P(PreviewsLitePageServerBrowserTest,
 
 IN_PROC_BROWSER_TEST_P(PreviewsLitePageServerBrowserTest,
                        DISABLE_ON_WIN_MAC(LitePagePreviewsReportSavings)) {
-  if (GetParam())
-    return;
   PrefService* prefs = browser()->profile()->GetPrefs();
   prefs->SetBoolean(data_reduction_proxy::prefs::kDataUsageReportingEnabled,
                     true);

chrome/browser/previews/previews_lite_page_serving_url_loader.cc

@@ -4,6 +4,7 @@
 
 #include "chrome/browser/previews/previews_lite_page_serving_url_loader.h"
 
+#include <stdint.h>
 #include <string>
 #include <utility>
 
@@ -88,6 +89,33 @@ void SetServerUnavailableFor(base::TimeDelta duration, int frame_tree_node_id) {
                      frame_tree_node_id));
 }
 
+void ReportDataSavingsOnUIThread(int64_t network_bytes,
+                                 int64_t original_bytes,
+                                 std::string host,
+                                 int frame_tree_node_id) {
+  auto* web_contents =
+      content::WebContents::FromFrameTreeNodeId(frame_tree_node_id);
+  // If the WebContents has been closed this may be null.
+  if (!web_contents)
+    return;
+
+  static_cast<PreviewsLitePageNavigationThrottleManager*>(
+      PreviewsServiceFactory::GetForProfile(
+          Profile::FromBrowserContext(web_contents->GetBrowserContext()))
+          ->previews_lite_page_decider())
+      ->ReportDataSavings(network_bytes, original_bytes, host);
+}
+
+void ReportDataSavings(int64_t network_bytes,
+                       int64_t original_bytes,
+                       std::string host,
+                       int frame_tree_node_id) {
+  base::PostTaskWithTraits(
+      FROM_HERE, {content::BrowserThread::UI, base::TaskPriority::USER_VISIBLE},
+      base::BindOnce(&ReportDataSavingsOnUIThread, network_bytes,
+                     original_bytes, std::move(host), frame_tree_node_id));
+}
+
 const base::TimeDelta kBlacklistDuration = base::TimeDelta::FromDays(30);
 
 // Used for mojo pipe size. Same constant as navigation code.
@@ -275,6 +303,17 @@ void PreviewsLitePageServingURLLoader::OnReceiveResponse(
   resource_response_ = base::MakeRefCounted<network::ResourceResponse>();
   resource_response_->head = head;
 
+  const int64_t ofcl =
+      data_reduction_proxy::GetDataReductionProxyOFCL(response_headers);
+  if (ofcl > 0) {
+    std::string original_url;
+    previews::ExtractOriginalURLFromLitePageRedirectURL(previews_url_,
+                                                        &original_url);
+
+    ReportDataSavings(response_headers->GetContentLength(), ofcl,
+                      GURL(original_url).host(), frame_tree_node_id_);
+  }
+
   url_loader_binding_.PauseIncomingMethodCallProcessing();
   std::move(result_callback_)
       .Run(ServingLoaderResult::kSuccess, base::nullopt, nullptr);