Report the duration of sampled tasks with histogram.

components/scheduler/renderer/task_duration_reporter.cc

Index: components/scheduler/renderer/task_duration_reporter.cc
diff --git a/components/scheduler/renderer/task_duration_reporter.cc b/components/scheduler/renderer/task_duration_reporter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b04c7d702d0aaa65760e3d359425daf379d4fc7c
--- /dev/null
+++ b/components/scheduler/renderer/task_duration_reporter.cc
@@ -0,0 +1,26 @@
+// Copyright 2016 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/scheduler/renderer/task_duration_reporter.h"
+
+#include "base/metrics/histogram_macros.h"
+
+namespace scheduler {
+namespace {
+const int kSampleInterval = 100;
+}
+
+TaskDurationReporter::TaskDurationReporter() : sample_count_(0) {}
+
+TaskDurationReporter::~TaskDurationReporter() {}
+
+void TaskDurationReporter::ReportTaskDuration(base::TimeDelta duration) {
+  ++sample_count_;
+  if (sample_count_ == kSampleInterval) {
+    UMA_HISTOGRAM_CUSTOM_COUNTS("RendererScheduler.TaskDuration",
+                                duration.InMicroseconds(), 1, 1000000, 100);
+    sample_count_ = 0;
+  }
+}
+}