Plumb experiment flags through page_load_metrics and add a new observer

components/page_load_metrics/renderer/metrics_render_frame_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 "components/page_load_metrics/renderer/metrics_render_frame_observer.h"
 
 #include <string>
 
 #include "base/time/time.h"
 #include "base/timer/timer.h"
@@ skipping 21 matching lines @@
 MetricsRenderFrameObserver::MetricsRenderFrameObserver(
     content::RenderFrame* render_frame)
     : content::RenderFrameObserver(render_frame) {}
 
 MetricsRenderFrameObserver::~MetricsRenderFrameObserver() {}
 
 void MetricsRenderFrameObserver::DidChangePerformanceTiming() {
   SendMetrics();
 }
 
+void MetricsRenderFrameObserver::DidUseExperiment(
+    blink::WebExperimentData data) {
+  DCHECK(page_timing_metrics_sender_);
+  page_timing_metrics_sender_->DidUseExperiment(data);
+}
+
 void MetricsRenderFrameObserver::DidCommitProvisionalLoad(
     bool is_new_navigation,
     bool is_same_page_navigation) {
   // Same-page navigations (e.g. an in-document navigation from a fragment
   // link) aren't full page loads, since they don't go to network to load the
   // main HTML resource. DidStartProvisionalLoad doesn't get invoked for same
   // page navigations, so we may still have an active
   // page_timing_metrics_sender_ at this point.
   if (is_same_page_navigation)
     return;
@@ skipping 75 matching lines @@
   return make_scoped_ptr(new base::OneShotTimer);
 }
 
 bool MetricsRenderFrameObserver::HasNoRenderFrame() const {
   bool no_frame = !render_frame() || !render_frame()->GetWebFrame();
   DCHECK(!no_frame);
   return no_frame;
 }
 
 }  // namespace page_load_metrics