Plumb experiment flags through page_load_metrics and add a new observer

components/page_load_metrics/renderer/page_timing_metrics_sender.h

 // 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.
 
 #ifndef COMPONENTS_PAGE_LOAD_METRICS_RENDERER_PAGE_TIMING_METRICS_SENDER_H_
 #define COMPONENTS_PAGE_LOAD_METRICS_RENDERER_PAGE_TIMING_METRICS_SENDER_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "components/page_load_metrics/common/page_load_timing.h"
+#include "third_party/WebKit/public/platform/WebLoadingBehaviorFlag.h"
 
 namespace base {
 class Timer;
 }  // namespace base
 
 namespace IPC {
 class Sender;
 }  // namespace IPC
 
 namespace page_load_metrics {
 
 // PageTimingMetricsSender is responsible for sending page load timing metrics
 // over IPC. PageTimingMetricsSender may coalesce sent IPCs in order to
 // minimize IPC contention.
 class PageTimingMetricsSender {
  public:
   PageTimingMetricsSender(IPC::Sender* ipc_sender,
                           int routing_id,
                           scoped_ptr<base::Timer> timer);
   ~PageTimingMetricsSender();
 
+  void DidObserveLoadingBehavior(blink::WebLoadingBehaviorFlag behavior);
   void Send(const PageLoadTiming& timing);
 
  protected:
   base::Timer* timer() const { return timer_.get(); }
 
  private:
+  void EnsureSendTimer();
   void SendNow();
 
   IPC::Sender* const ipc_sender_;
   const int routing_id_;
   scoped_ptr<base::Timer> timer_;
   PageLoadTiming last_timing_;
 
+  // The the sender keep track of metadata as it comes in, because the sender is
+  // scoped to a single committed load.
+  PageLoadMetadata metadata_;
+
   DISALLOW_COPY_AND_ASSIGN(PageTimingMetricsSender);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // COMPONENTS_PAGE_LOAD_METRICS_RENDERER_PAGE_TIMING_METRICS_SENDER_H_