Report the duration of sampled tasks with histogram.

components/scheduler/renderer/renderer_scheduler_impl.h

 // Copyright 2014 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_SCHEDULER_RENDERER_RENDERER_SCHEDULER_IMPL_H_
 #define COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_IMPL_H_
 
 #include "base/atomicops.h"
 #include "base/macros.h"
 #include "base/synchronization/lock.h"
 #include "components/scheduler/base/long_task_tracker.h"
 #include "components/scheduler/base/pollable_thread_safe_flag.h"
 #include "components/scheduler/base/queueing_time_estimator.h"
 #include "components/scheduler/base/task_time_tracker.h"
 #include "components/scheduler/child/idle_helper.h"
 #include "components/scheduler/child/scheduler_helper.h"
 #include "components/scheduler/renderer/deadline_task_runner.h"
 #include "components/scheduler/renderer/idle_time_estimator.h"
 #include "components/scheduler/renderer/render_widget_signals.h"
 #include "components/scheduler/renderer/renderer_scheduler.h"
 #include "components/scheduler/renderer/task_cost_estimator.h"
+#include "components/scheduler/renderer/task_duration_reporter.h"
 #include "components/scheduler/renderer/throttling_helper.h"
 #include "components/scheduler/renderer/user_model.h"
 #include "components/scheduler/renderer/web_view_scheduler_impl.h"
 #include "components/scheduler/scheduler_export.h"
 
 namespace base {
 namespace trace_event {
 class ConvertableToTraceFormat;
 }
 }
@@ skipping 431 matching lines @@
   }
 
   // Don't access compositor_thread_only_, instead use CompositorThreadOnly().
   CompositorThreadOnly compositor_thread_only_;
   CompositorThreadOnly& CompositorThreadOnly() {
     compositor_thread_only_.CheckOnValidThread();
     return compositor_thread_only_;
   }
 
   PollableThreadSafeFlag policy_may_need_update_;
+
+  TaskDurationReporter duration_reporter_;

[tdresser, 2016/07/27 18:04:25]

I think we can put this in MainThreadOnly(), to make it clear what thread this
is accessed from.

[sunyunjia, 2016/07/27 19:51:04]

Done.

+
   base::WeakPtrFactory<RendererSchedulerImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererSchedulerImpl);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_IMPL_H_