Adding UMA on page load size for pages with Media

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 86 matching lines @@
     host->GetWidget()->RemoveInputEventObserver(this);
 }
 
 void MetricsWebContentsObserver::RenderViewHostChanged(
     content::RenderViewHost* old_host,
     content::RenderViewHost* new_host) {
   UnregisterInputEventObserver(old_host);
   RegisterInputEventObserver(new_host);
 }
 
+void MetricsWebContentsObserver::MediaStartedPlaying(
+    const content::WebContentsObserver::MediaPlayerInfo& video_type,
+    const content::WebContentsObserver::MediaPlayerId& id) {
+  if (committed_load_)

[Bryan McQuade, 2017/03/15 01:59:46]

we should just make sure that the top-level frame matches the currently
committed main frame first, similar to what we do in OnTimingUpdated. something
like

if (id.first>GetRenderViewHost()->GetMainFrame() !=
          web_contents()->GetMainFrame()) {
  // received a media notification for a different frame.
  // this may happen in cases where media starts playing in a document
  // that was navigated away from. ignore it.
  return;
}

+    committed_load_->MediaStartedPlaying(
+        video_type, id.first == web_contents()->GetMainFrame());
+}
+
 bool MetricsWebContentsObserver::OnMessageReceived(
     const IPC::Message& message,
     content::RenderFrameHost* render_frame_host) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP_WITH_PARAM(MetricsWebContentsObserver, message,
                                    render_frame_host)
     IPC_MESSAGE_HANDLER(PageLoadMetricsMsg_TimingUpdated, OnTimingUpdated)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
@@ skipping 441 matching lines @@
     content::NavigationHandle* navigation_handle) const {
   DCHECK(navigation_handle->IsInMainFrame());
   DCHECK(!navigation_handle->HasCommitted() ||
          !navigation_handle->IsSameDocument());
 
   return BrowserPageTrackDecider(embedder_interface_.get(), web_contents(),
                                  navigation_handle).ShouldTrack();
 }
 
 }  // namespace page_load_metrics