patch from issue 1063083002 at patchset 20001 (http://crrev.com/1063083002#ps20001)

Source/platform/heap/Heap.h

Index: Source/platform/heap/Heap.h
diff --git a/Source/platform/heap/Heap.h b/Source/platform/heap/Heap.h
index 5bd5addd0d4027a38ae0463c9cf356c07053c2a5..9894c769c7a152ed0ff1e18702b60db3ce9f97fd 100644
--- a/Source/platform/heap/Heap.h
+++ b/Source/platform/heap/Heap.h
@@ -1021,26 +1021,11 @@ public:
     static size_t allocatedSpace() { return acquireLoad(&s_allocatedSpace); }
     static size_t estimatedLiveObjectSize() { return acquireLoad(&s_estimatedLiveObjectSize); }
     static void setEstimatedLiveObjectSize(size_t size) { releaseStore(&s_estimatedLiveObjectSize, size); }
+    static size_t externalObjectSizeAtLastGC() { return acquireLoad(&s_externalObjectSizeAtLastGC); }
 
     static double estimatedMarkingTime();
     static void reportMemoryUsageHistogram();
 
-    // On object allocation, register the object's externally allocated memory.
-    static void increaseExternallyAllocatedBytes(size_t);
-    static size_t externallyAllocatedBytes() { return acquireLoad(&s_externallyAllocatedBytes); }
-
-    // On object tracing, register the object's externally allocated memory (as still live.)
-    static void increaseExternallyAllocatedBytesAlive(size_t delta)
-    {
-        ASSERT(ThreadState::current()->isInGC());
-        s_externallyAllocatedBytesAlive += delta;
-    }
-    static size_t externallyAllocatedBytesAlive() { return s_externallyAllocatedBytesAlive; }
-
-    static void requestUrgentGC();
-    static void clearUrgentGC() { releaseStore(&s_requestedUrgentGC, 0); }
-    static bool isUrgentGCRequested() { return acquireLoad(&s_requestedUrgentGC); }
-
 private:
     // A RegionTree is a simple binary search tree of PageMemoryRegions sorted
     // by base addresses.
@@ -1079,9 +1064,7 @@ private:
     static size_t s_allocatedObjectSize;
     static size_t s_markedObjectSize;
     static size_t s_estimatedLiveObjectSize;
-    static size_t s_externallyAllocatedBytes;
-    static size_t s_externallyAllocatedBytesAlive;
-    static unsigned s_requestedUrgentGC;
+    static size_t s_externalObjectSizeAtLastGC;
     static double s_estimatedMarkingTimePerByte;
 
     friend class ThreadState;
@@ -1478,28 +1461,6 @@ Address Heap::reallocate(void* previous, size_t size)
     return address;
 }
 
-inline void Heap::increaseExternallyAllocatedBytes(size_t delta)
-{
-    // Flag GC urgency on a 50% increase in external allocation
-    // since the last GC, but not for less than 100M.
-    //
-    // FIXME: consider other, 'better' policies (e.g., have the count of
-    // heap objects with external allocations be taken into
-    // account, ...) The overall goal here is to trigger a
-    // GC such that it considerably lessens memory pressure
-    // for a renderer process, when absolutely needed.
-    size_t externalBytesAllocatedSinceLastGC = atomicAdd(&s_externallyAllocatedBytes, static_cast<long>(delta));
-    if (LIKELY(externalBytesAllocatedSinceLastGC < 100 * 1024 * 1024))
-        return;
-
-    if (UNLIKELY(isUrgentGCRequested()))
-        return;
-
-    size_t externalBytesAliveAtLastGC = externallyAllocatedBytesAlive();
-    if (UNLIKELY(externalBytesAllocatedSinceLastGC > externalBytesAliveAtLastGC / 2))
-        Heap::requestUrgentGC();
-}
-
 template<bool needsTracing, WTF::WeakHandlingFlag weakHandlingFlag, WTF::ShouldWeakPointersBeMarkedStrongly strongify, typename T, typename Traits> struct CollectionBackingTraceTrait;
 template<typename T, typename Traits = WTF::VectorTraits<T>> class HeapVectorBacking;
 template<typename Table> class HeapHashTableBacking {