Oilpan: Add TRACE_EVENT0 to ThreadState::waitUntilSweepersDone.

Source/platform/heap/ThreadState.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1011 matching lines @@
 void ThreadState::unregisterSweepingTask()
 {
     MutexLocker locker(m_sweepMutex);
     ASSERT(m_numberOfSweeperTasks > 0);
     if (!--m_numberOfSweeperTasks)
         m_sweepThreadCondition.signal();
 }
 
 void ThreadState::waitUntilSweepersDone()
 {
+    TRACE_EVENT0("blink_gc", "ThreadState::waitUntilSweepersDone");
     MutexLocker locker(m_sweepMutex);
     while (m_numberOfSweeperTasks > 0)
         m_sweepThreadCondition.wait(m_sweepMutex);
 }
 
 
 class SweepNonFinalizedHeapTask final : public WebThread::Task {
 public:
     SweepNonFinalizedHeapTask(ThreadState* state, BaseHeap* heap, HeapStats* stats)
         : m_threadState(state)
@@ skipping 231 matching lines @@
             return gcInfo;
         }
     }
     if (needLockForIteration)
         threadAttachMutex().unlock();
     return 0;
 }
 #endif
 
 }