Report the duration of sampled tasks with histogram.

components/scheduler/BUILD.gn

 # 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.
 
 # GYP version: components/scheduler.gypi:scheduler
+import("//testing/test.gni")

[majidvp, 2016/07/27 13:50:59]

You should not need to import 'test.gni'. 
To add a dependency, add the target in the deps.

[sunyunjia, 2016/07/27 17:28:42]

Done.

+
 component("scheduler") {
   sources = [
     "base/cancelable_closure_holder.cc",
     "base/cancelable_closure_holder.h",
     "base/enqueue_order.cc",
     "base/enqueue_order.h",
     "base/lazy_now.cc",
     "base/lazy_now.h",
     "base/long_task_tracker.cc",
     "base/long_task_tracker.h",
@@ skipping 51 matching lines @@
     "renderer/idle_time_estimator.cc",
     "renderer/idle_time_estimator.h",
     "renderer/render_widget_scheduling_state.cc",
     "renderer/render_widget_scheduling_state.h",
     "renderer/render_widget_signals.cc",
     "renderer/render_widget_signals.h",
     "renderer/renderer_scheduler.cc",
     "renderer/renderer_scheduler.h",
     "renderer/renderer_scheduler_impl.cc",
     "renderer/renderer_scheduler_impl.h",
+    "renderer/renderer_task_duration.cc",
+    "renderer/renderer_task_duration.h",
     "renderer/renderer_web_scheduler_impl.cc",
     "renderer/renderer_web_scheduler_impl.h",
     "renderer/task_cost_estimator.cc",
     "renderer/task_cost_estimator.h",
     "renderer/throttled_time_domain.cc",
     "renderer/throttled_time_domain.h",
     "renderer/throttling_helper.cc",
     "renderer/throttling_helper.h",
     "renderer/user_model.cc",
     "renderer/user_model.h",
@@ skipping 55 matching lines @@
     "child/scheduler_tqm_delegate_for_test.cc",
     "child/scheduler_tqm_delegate_for_test.h",
     "child/scheduler_tqm_delegate_impl_unittest.cc",
     "child/webthread_impl_for_worker_scheduler_unittest.cc",
     "child/worker_scheduler_impl_unittest.cc",
     "renderer/auto_advancing_virtual_time_domain_unittest.cc",
     "renderer/deadline_task_runner_unittest.cc",
     "renderer/idle_time_estimator_unittest.cc",
     "renderer/render_widget_signals_unittest.cpp",
     "renderer/renderer_scheduler_impl_unittest.cc",
+    "renderer/renderer_task_duration_unittest.cc",
     "renderer/task_cost_estimator_unittest.cc",
     "renderer/throttling_helper_unittest.cc",
     "renderer/user_model_unittest.cc",
     "renderer/web_view_scheduler_impl_unittest.cc",
     "renderer/webthread_impl_for_renderer_scheduler_unittest.cc",
   ]
 
   deps = [
     ":scheduler",
     "//base/test:test_support",
     "//cc:test_support",
     "//testing/gmock",
     "//testing/gtest",

[majidvp, 2016/07/27 13:50:59]

Add you dependencies here if necessary. The testing/gtest is 
already here so I don't think you need to add it.

[sunyunjia, 2016/07/27 17:28:42]

Acknowledged.

   ]
 }
 
 # GYP version: components/scheduler.gypi:scheduler_test_support
 static_library("test_support") {
   testonly = true
 
   sources = [
     "test/lazy_scheduler_message_loop_delegate_for_tests.cc",
     "test/lazy_scheduler_message_loop_delegate_for_tests.h",
     "test/renderer_scheduler_test_support.cc",
     "test/renderer_scheduler_test_support.h",
   ]
 
   deps = [
     "//third_party/WebKit/public:blink",
   ]
 
   public_deps = [
     ":scheduler",
     "//base",
   ]
 }