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

third_party/WebKit/Source/platform/scheduler/base/task_time_tracker.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_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_TIME_TRACKER_H_
-#define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_TIME_TRACKER_H_
-
-#include "base/time/time.h"
-#include "public/platform/WebCommon.h"
-
-namespace blink {
-namespace scheduler {
-
-class BLINK_PLATFORM_EXPORT TaskTimeTracker {
- public:
-  TaskTimeTracker() {}
-  virtual ~TaskTimeTracker() {}
-
-  virtual void ReportTaskTime(base::TimeTicks startTime,
-                              base::TimeTicks endTime) = 0;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(TaskTimeTracker);
-};
-
-}  // namespace scheduler
-}  // namespace blink
-
-#endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_TIME_TRACKER_H_