Report DOM partitionAlloc size to V8 GC.

Source/bindings/v8/V8GCController.cpp

Index: Source/bindings/v8/V8GCController.cpp
diff --git a/Source/bindings/v8/V8GCController.cpp b/Source/bindings/v8/V8GCController.cpp
index dfea224c4ef72765891958d54bef73313bc0727d..4c471ae0f99fdafe9819a0fab9b2554c02592c7d 100644
--- a/Source/bindings/v8/V8GCController.cpp
+++ b/Source/bindings/v8/V8GCController.cpp
@@ -48,6 +48,7 @@
 #include "core/html/imports/HTMLImportsController.h"
 #include "core/inspector/InspectorTraceEvents.h"
 #include "core/svg/SVGElement.h"
+#include "platform/Partitions.h"
 #include "platform/TraceEvent.h"
 #include <algorithm>
 
@@ -437,4 +438,18 @@ void V8GCController::collectGarbage(v8::Isolate* isolate)
     scriptState->disposePerContextData();
 }
 
+void V8GCController::reportDOMMemoryUsageToV8(v8::Isolate* isolate)
+{
+    if (!isMainThread())
+        return;
+
+    static size_t lastUsageReportedToV8 = 0;
+
+    size_t currentUsage = Partitions::currentDOMMemoryUsage();
+    ssize_t diff = static_cast<ssize_t>(currentUsage) - static_cast<ssize_t>(lastUsageReportedToV8);
+    isolate->AdjustAmountOfExternalAllocatedMemory(diff);

[Tom Sepez, 2014/06/05 17:58:08]

nit: down the road, you'd probably be happier with an V8 API that took an
absolute. 

+
+    lastUsageReportedToV8 = currentUsage;
+}
+
 }  // namespace WebCore