Prevent GCs when constructing GC mixin objects.

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 218 matching lines @@
     , m_persistents(adoptPtr(new PersistentAnchor()))
     , m_startOfStack(reinterpret_cast<intptr_t*>(StackFrameDepth::getStackStart()))
     , m_endOfStack(reinterpret_cast<intptr_t*>(StackFrameDepth::getStackStart()))
     , m_safePointScopeMarker(nullptr)
     , m_atSafePoint(false)
     , m_interruptors()
     , m_hasPendingIdleTask(false)
     , m_didV8GCAfterLastGC(false)
     , m_sweepForbidden(false)
     , m_noAllocationCount(0)
+    , m_gcForbiddenCount(0)
     , m_isTerminating(false)
     , m_shouldFlushHeapDoesNotContainCache(false)
     , m_collectionRate(1.0)
     , m_gcState(NoGCScheduled)
     , m_traceDOMWrappers(nullptr)
 #if defined(ADDRESS_SANITIZER)
     , m_asanFakeStack(__asan_get_current_fake_stack())
 #endif
 #if ENABLE(GC_PROFILING)
     , m_nextFreeListSnapshotTime(-std::numeric_limits<double>::infinity())
@@ skipping 413 matching lines @@
     // but not for less than 512 KB.
     size_t newSize = Heap::allocatedObjectSize();
     return newSize >= 512 * 1024 && newSize > Heap::markedObjectSize() / 2;
 #endif
 }
 
 // FIXME: We should improve the GC heuristics.
 // These heuristics affect performance significantly.
 bool ThreadState::shouldForceConservativeGC()
 {
+    if (UNLIKELY(m_gcForbiddenCount))
+        return false;
+
     size_t newSize = Heap::allocatedObjectSize();
     if (newSize >= 300 * 1024 * 1024) {
         // If we consume too much memory, trigger a conservative GC
         // on a 50% increase in size since the last GC. This is a safe guard
         // to avoid OOM.
         return newSize > Heap::markedObjectSize() / 2;
     }
     if (m_didV8GCAfterLastGC && m_collectionRate > 0.5) {
         // If we had a V8 GC after the last Oilpan GC and the last collection
         // rate was higher than 50%, trigger a conservative GC on a 200%
@@ skipping 585 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