Oilpan: Trace ThreadState::performIdleGC() function for better debuggability.

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 661 matching lines @@
 }
 
 void ThreadState::performIdleGC(double deadlineSeconds)
 {
     ASSERT(isMainThread());
 
     if (gcState() != IdleGCScheduled)
         return;
 
     double idleDeltaInSeconds = deadlineSeconds - Platform::current()->monotonicallyIncreasingTime();
+    TRACE_EVENT2("blink_gc", "ThreadState::performIdleGC", "idleDeltaInSeconds", idleDeltaInSeconds, "estimatedMarkingTime", Heap::estimatedMarkingTime());
     if (idleDeltaInSeconds <= Heap::estimatedMarkingTime() && !Platform::current()->currentThread()->scheduler()->canExceedIdleDeadlineIfRequired()) {
         // If marking is estimated to take longer than the deadline and we can't
         // exceed the deadline, then reschedule for the next idle period.
         scheduleIdleGC();
         return;
     }
 
     Heap::collectGarbage(NoHeapPointersOnStack, GCWithoutSweep, Heap::IdleGC);
 }
 
@@ skipping 776 matching lines @@
         json->beginArray(it->key.ascii().data());
         for (size_t age = 0; age <= maxHeapObjectAge; ++age)
             json->pushInteger(it->value.ages[age]);
         json->endArray();
     }
     TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(TRACE_DISABLED_BY_DEFAULT("blink_gc"), statsName, this, json.release());
 }
 #endif
 
 } // namespace blink