Adding UMA on page load size for pages with Media

chrome/browser/page_load_metrics/page_load_tracker.h

 // Copyright 2016 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 CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/optional.h"
 #include "base/time/time.h"
 #include "chrome/browser/page_load_metrics/page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/user_input_tracker.h"
 #include "chrome/common/page_load_metrics/page_load_timing.h"
 #include "content/public/browser/global_request_id.h"
+#include "content/public/browser/web_contents_observer.h"
 #include "ui/base/page_transition_types.h"
 
 class GURL;
 
 namespace blink {
 class WebInputEvent;
 }  // namespace blink
 
 namespace content {
 class NavigationHandle;
@@ skipping 196 matching lines @@
   UserInputTracker* input_tracker() { return &input_tracker_; }
 
   // Whether this PageLoadTracker has a navigation GlobalRequestID that matches
   // the given request_id. This method will return false before
   // WillProcessNavigationResponse has been invoked, as PageLoadTracker doesn't
   // know its GlobalRequestID until WillProcessNavigationResponse has been
   // invoked.
   bool HasMatchingNavigationRequestID(
       const content::GlobalRequestID& request_id) const;
 
+  // Invoked when a media element starts playing.
+  void MediaStartedPlaying(
+      const content::WebContentsObserver::MediaPlayerInfo& video_type,
+      bool is_in_main_frame);
+
  private:
   // This function converts a TimeTicks value taken in the browser process
   // to navigation_start_ if:
   // - base::TimeTicks is not comparable across processes because the clock
   // is not system wide monotonic.
   // - *event_time < navigation_start_
   void ClampBrowserTimestampIfInterProcessTimeTickSkew(
       base::TimeTicks* event_time);
 
   void UpdatePageEndInternal(PageEndReason page_end_reason,
@@ skipping 84 matching lines @@
   PageLoadMetricsEmbedderInterface* const embedder_interface_;
 
   std::vector<std::unique_ptr<PageLoadMetricsObserver>> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(PageLoadTracker);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_TRACKER_H_