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

third_party/WebKit/public/platform/WebThread.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
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  * modification, are permitted provided that the following conditions
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  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 #ifndef WebThread_h
 #define WebThread_h
 
 #include "WebCommon.h"
+
 #include <stdint.h>
 
 namespace blink {
+namespace scheduler {
+class TaskTimeObserver;
+}
+
 class WebScheduler;
 class WebTaskRunner;
 
 // Always an integer value.
 typedef uintptr_t PlatformThreadId;
 
 // Provides an interface to an embedder-defined thread implementation.
 //
 // Deleting the thread blocks until all pending, non-delayed tasks have been
 // run.
@@ skipping 14 matching lines @@
         virtual void didProcessTask() = 0;
     };
 
 
     // Returns a WebTaskRunner bound to the underlying scheduler's default task queue.
     virtual WebTaskRunner* getWebTaskRunner() { return nullptr; }
 
     virtual bool isCurrentThread() const = 0;
     virtual PlatformThreadId threadId() const { return 0; }
 
+    // TaskObserver is an object that receives task notifications from the MessageLoop
+    // NOTE: TaskObserver implementation should be extremely fast!
+    // This API is performance sensitive. Use only if you have a compelling reason.
     virtual void addTaskObserver(TaskObserver*) { }
     virtual void removeTaskObserver(TaskObserver*) { }
 
+    // TaskTimeObserver is an object that receives notifications for
+    // CPU time spent in each top-level MessageLoop task.
+    // NOTE: TaskTimeObserver implementation should be extremely fast!
+    // This API is performance sensitive. Use only if you have a compelling reason.
+    virtual void addTaskTimeObserver(scheduler::TaskTimeObserver*) {}
+    virtual void removeTaskTimeObserver(scheduler::TaskTimeObserver*) {}
+
     // Returns the scheduler associated with the thread.
     virtual WebScheduler* scheduler() const = 0;
 
     virtual ~WebThread() { }
 };
 
 } // namespace blink
 
 #endif