Report the duration of sampled tasks with histogram.

components/scheduler/BUILD.gn

Index: components/scheduler/BUILD.gn
diff --git a/components/scheduler/BUILD.gn b/components/scheduler/BUILD.gn
index 035feb177df0ef23624e7cc02126a3e299486b3b..f9784aa6b6182779bc5e51c6a038eb9994783041 100644
--- a/components/scheduler/BUILD.gn
+++ b/components/scheduler/BUILD.gn
@@ -3,6 +3,8 @@
 # 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",
@@ -74,6 +76,8 @@ component("scheduler") {
     "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",
@@ -149,6 +153,7 @@ source_set("unit_tests") {
     "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",