Move and rename TaskTimeTracker to public interface exposed to WebThread, use in WebPerf Agent.

third_party/WebKit/public/platform/scheduler/base/task_time_observer.h

+// 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.
+
+#ifndef THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_BASE_TASK_TIME_OBSERVER_H_
+#define THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_BASE_TASK_TIME_OBSERVER_H_
+
+#include "base/time/time.h"
+#include "public/platform/WebCommon.h"
+
+namespace blink {
+namespace scheduler {
+
+class BLINK_PLATFORM_EXPORT TaskTimeObserver {
+ public:
+  TaskTimeObserver() {}
+  virtual ~TaskTimeObserver() {}
+
+  virtual void ReportTaskTime(double startTime, double endTime) = 0;

[pfeldman, 2016/08/29 17:23:08]

reportTaskTime (from lower case). Also, do you need start and end or the task
length?

[panicker, 2016/08/29 17:46:23]

This is still following pre-Blink Scheduler code style to be consistent with
code in third_party/WebKit/public/platform/scheduler/
caseq had a comment about switching Scheduler over to Blink style - but not sure
of timeline there.

[pfeldman, 2016/08/29 17:52:54]

Okay. What about the startTime/endTime vs length? Do you envision reporting the
monotonic times to the users on the perf timeline?

[panicker, 2016/08/29 18:01:32]

Oops yeah - I do need startTime / EndTime as it's needed by the PerformanceEntry
ctor:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/timing/Pe...
https://www.w3.org/TR/performance-timeline-2/#the-performanceentry-interface

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TaskTimeObserver);
+};
+
+}  // namespace scheduler
+}  // namespace blink
+
+#endif  // THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_BASE_TASK_TIME_OBSERVER_H_