Report expected task queueing time via UMA

components/scheduler/base/task_time_tracker.cc

Index: components/scheduler/base/task_time_tracker.cc
diff --git a/components/scheduler/base/task_time_tracker.cc b/components/scheduler/base/task_time_tracker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d4957730f20dabf26d2bc5dd335486dfa63c5d09
--- /dev/null
+++ b/components/scheduler/base/task_time_tracker.cc
@@ -0,0 +1,37 @@
+// 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/base/task_time_tracker.h"
+
+#include "base/metrics/histogram_macros.h"
+#include "base/trace_event/trace_event.h"
+
+namespace scheduler {
+
+TaskTimeTracker::TaskTimeTracker()
+    : task_time_observer_(nullptr),
+      queueing_time_estimator_(this, base::TimeDelta::FromSeconds(1)) {}
+
+TaskTimeTracker::~TaskTimeTracker() {}
+
+void TaskTimeTracker::SetObserver(TaskTimeObserver* task_time_observer) {
+  task_time_observer_ = task_time_observer;
+}
+
+void TaskTimeTracker::OnQueueingTimeForWindowEstimated(
+    base::TimeDelta queueing_time) {
+  UMA_HISTOGRAM_TIMES("RendererScheduler.ExpectedTaskQueueingDuration",
+                      queueing_time);
+  TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
+                 "estimated_queueing_time_for_window",
+                 queueing_time.InMillisecondsF());
+}
+
+void TaskTimeTracker::ReportTaskTime(
+    base::TimeTicks task_start_time, base::TimeTicks task_end_time) {
+  queueing_time_estimator_.OnToplevelTaskCompleted(task_start_time,
+                                                   task_end_time);
+}
+
+} // scheduler