Allow Oilpan heap objects account for their external allocations.

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 e3289815642856b4b9a2cba5d92f03d2e2b0a163..b4530e9724fcfed364a356fcd5f5c6257d553e1d 100644
--- a/Source/platform/heap/Heap.h
+++ b/Source/platform/heap/Heap.h
@@ -1009,8 +1009,25 @@ public:
     static void increaseAllocatedSpace(size_t delta) { atomicAdd(&s_allocatedSpace, static_cast<long>(delta)); }
     static void decreaseAllocatedSpace(size_t delta) { atomicSubtract(&s_allocatedSpace, static_cast<long>(delta)); }
     static size_t allocatedSpace() { return acquireLoad(&s_allocatedSpace); }
+
     static double estimatedMarkingTime();
 
+    // On object allocation, register its externally allocated memory.
+    static void increaseExternallyAllocatedBytes(size_t);
+    static size_t externallyAllocatedBytes() { return acquireLoad(&s_externallyAllocatedBytes); }
+
+    // On object tracing, register its 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() { releaseStore(&s_requestedUrgentGC, 1); }
+    static void clearUrgentGC() { releaseStore(&s_requestedUrgentGC, 0); }
+    static bool isGCUrgentlyRequested() { return acquireLoad(&s_requestedUrgentGC); }
+
 private:
     // A RegionTree is a simple binary search tree of PageMemoryRegions sorted
     // by base addresses.
@@ -1031,8 +1048,8 @@ private:
         RegionTree* m_right;
     };
 
-    static void resetAllocatedObjectSize() { ASSERT(ThreadState::current()->isInGC()); s_allocatedObjectSize = 0; }
-    static void resetMarkedObjectSize() { ASSERT(ThreadState::current()->isInGC()); s_markedObjectSize = 0; }
+    // Reset counters that track live and allocated-since-last-GC sizes.
+    static void resetHeapCounters();
 
     static Visitor* s_markingVisitor;
     static CallbackStack* s_markingStack;
@@ -1048,6 +1065,10 @@ private:
     static size_t s_allocatedSpace;
     static size_t s_allocatedObjectSize;
     static size_t s_markedObjectSize;
+    static size_t s_externallyAllocatedBytes;
+    static size_t s_externallyAllocatedBytesAlive;
+    static unsigned s_requestedUrgentGC;
+
     friend class ThreadState;
 };