Allow Oilpan heap objects account for their external allocations.

Source/platform/heap/ThreadState.h

 /*
  * 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 325 matching lines @@
     void schedulePreciseGC();
     void scheduleGCIfNeeded();
     void setGCState(GCState);
     GCState gcState() const;
     bool isInGC() const { return gcState() == GCRunning; }
     bool isSweepingInProgress() const
     {
         return gcState() == Sweeping || gcState() == SweepingAndPreciseGCScheduled || gcState() == SweepingAndIdleGCScheduled;
     }
 
+    bool isSweepingScheduled() const
+    {
+        return gcState() == SweepingAndPreciseGCScheduled || gcState() == SweepingAndIdleGCScheduled;
+    }
+
     void preGC();
     void postGC(GCType);
 
     // Support for disallowing allocation. Mainly used for sanity
     // checks asserts.
     bool isAllocationAllowed() const { return !isAtSafePoint() && !m_noAllocationCount; }
     void enterNoAllocationScope() { m_noAllocationCount++; }
     void leaveNoAllocationScope() { m_noAllocationCount--; }
 
     // Before performing GC the thread-specific heap state should be
@@ skipping 431 matching lines @@
         m_locked = false;
     }
 
     MutexBase& m_mutex;
     bool m_locked;
 };
 
 } // namespace blink
 
 #endif // ThreadState_h