Instantiate PageLoadTrackers for prerenders

chrome/browser/page_load_metrics/metrics_web_contents_observer.cc

 // Copyright 2015 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 "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 
 #include <algorithm>
 #include <ostream>
 #include <string>
 #include <utility>
@@ skipping 283 matching lines @@
       abort_user_initiated_(false),
       started_in_foreground_(in_foreground),
       page_transition_(navigation_handle->GetPageTransition()),
       num_cache_requests_(0),
       num_network_requests_(0),
       user_gesture_(IsNavigationUserInitiated(navigation_handle)),
       aborted_chain_size_(aborted_chain_size),
       aborted_chain_size_same_url_(aborted_chain_size_same_url),
       embedder_interface_(embedder_interface) {
   DCHECK(!navigation_handle->HasCommitted());
+  if (embedder_interface_->IsPrerendering(
+          navigation_handle->GetWebContents())) {
+    DCHECK(!started_in_foreground_);
+    // For the time being, we do not track prerenders. See crbug.com/648338 for
+    // details.
+    StopTracking();
+    return;
+  }
+
   embedder_interface_->RegisterObservers(this);
   for (const auto& observer : observers_) {
     observer->OnStart(navigation_handle, currently_committed_url,
                       started_in_foreground_);
   }
 }
 
 PageLoadTracker::~PageLoadTracker() {
   if (app_entered_background_) {
     RecordAppBackgroundPageLoadCompleted(true);
@@ skipping 435 matching lines @@
     } else if (last_aborted->aborted_chain_size_same_url() > 0) {
       LogAbortChainSameURLHistogram(
           last_aborted->aborted_chain_size_same_url());
     }
     chain_size = last_aborted->aborted_chain_size() + 1;
   }
 
   if (!ShouldTrackNavigation(navigation_handle))
     return;
 
-  // TODO(bmcquade): add support for tracking prerendered pages when they become
-  // visible.
-  if (embedder_interface_->IsPrerendering(web_contents()))
-    return;
-
   // Pass in the last committed url to the PageLoadTracker. If the MWCO has
   // never observed a committed load, use the last committed url from this
   // WebContent's opener. This is more accurate than using referrers due to
   // referrer sanitizing and origin referrers. Note that this could potentially
   // be inaccurate if the opener has since navigated.
   content::WebContents* opener = web_contents()->GetOpener();
   const GURL& opener_url =
       !has_navigated_ && opener
           ? web_contents()->GetOpener()->GetLastCommittedURL()
           : GURL::EmptyGURL();
@@ skipping 293 matching lines @@
     content::NavigationHandle* navigation_handle) const {
   DCHECK(navigation_handle->IsInMainFrame());
   DCHECK(!navigation_handle->HasCommitted() ||
          !navigation_handle->IsSamePage());
 
   return BrowserPageTrackDecider(embedder_interface_.get(), web_contents(),
                                  navigation_handle).ShouldTrack();
 }
 
 }  // namespace page_load_metrics