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

third_party/WebKit/Source/platform/scheduler/child/scheduler_helper.h

Index: third_party/WebKit/Source/platform/scheduler/child/scheduler_helper.h
diff --git a/third_party/WebKit/Source/platform/scheduler/child/scheduler_helper.h b/third_party/WebKit/Source/platform/scheduler/child/scheduler_helper.h
index c1991af6ebc4491343b17c6bb4e2edf7a0e82317..781677de77b3bac7676c0f3878026a5f8595cf2a 100644
--- a/third_party/WebKit/Source/platform/scheduler/child/scheduler_helper.h
+++ b/third_party/WebKit/Source/platform/scheduler/child/scheduler_helper.h
@@ -11,6 +11,7 @@
 #include "base/time/tick_clock.h"
 #include "platform/scheduler/base/task_queue_manager.h"
 #include "platform/scheduler/base/task_queue_selector.h"
+#include "public/platform/WebThread.h"
 
 namespace base {
 class TickClock;
@@ -63,6 +64,16 @@ class BLINK_PLATFORM_EXPORT SchedulerHelper
       task_queue_manager_->SetTaskTimeTracker(task_time_tracker);
   }
 
+  void AddTaskTimeObserver(WebThread::TaskTimeObserver* task_time_observer) {
+    if (task_queue_manager_)
+      task_queue_manager_->AddTaskTimeObserver(task_time_observer);
+  }
+
+  void RemoveTaskTimeObserver(WebThread::TaskTimeObserver* task_time_observer) {
+    if (task_queue_manager_)
+      task_queue_manager_->RemoveTaskTimeObserver(task_time_observer);
+  }
+
   // Shuts down the scheduler by dropping any remaining pending work in the work
   // queues. After this call any work posted to the task runners will be
   // silently dropped.