Add NavigationToFirstContentfulPaint UMA for ServiceWorker controlled pages.

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 23 matching lines @@
     : content::RenderFrameObserver(render_frame) {}
 
 MetricsRenderFrameObserver::~MetricsRenderFrameObserver() {}
 
 void MetricsRenderFrameObserver::DidChangePerformanceTiming() {
   SendMetrics();
 }
 
 void MetricsRenderFrameObserver::DidObserveLoadingBehavior(
     blink::WebLoadingBehaviorFlag behavior) {
+  if (!ShouldSendMetrics())

[Charlie Harrison, 2016/04/14 13:29:56]

Actually, I think I retract my comment. This won't work for an in-page
navigation.

Additionally, the logic in DidChangePerformanceTiming looks at
!page_timing_metrics_sender_, so perhaps it's best to do the conservative check
for consistency. I'm adding this check because clusterfuzz found the bug in my
CL.

[horo, 2016/04/14 14:01:30]

Changed to check page_timing_metrics_sender_

+    return;
   DCHECK(page_timing_metrics_sender_);
   page_timing_metrics_sender_->DidObserveLoadingBehavior(behavior);
 }
 
 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
@@ skipping 86 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