Oilpan: allow StoppingOtherThreads GC state transition.

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 738 matching lines @@
     }
 
     setGCState(PreciseGCScheduled);
 }
 
 void ThreadState::setGCState(GCState gcState)
 {
     switch (gcState) {
     case NoGCScheduled:
         checkThread();
-        RELEASE_ASSERT(m_gcState == Sweeping || m_gcState == SweepingAndIdleGCScheduled);
+        RELEASE_ASSERT(m_gcState == StoppingOtherThreads || m_gcState == Sweeping || m_gcState == SweepingAndIdleGCScheduled);
         break;
     case IdleGCScheduled:
     case PreciseGCScheduled:
     case GCScheduledForTesting:
         checkThread();
         RELEASE_ASSERT(m_gcState == NoGCScheduled || m_gcState == IdleGCScheduled || m_gcState == PreciseGCScheduled || m_gcState == GCScheduledForTesting || m_gcState == StoppingOtherThreads || m_gcState == SweepingAndPreciseGCScheduled);
         completeSweep();
         break;
     case StoppingOtherThreads:
         checkThread();
@@ skipping 495 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