Do V8 GC ASAP if system memory is pressured[reland]

third_party/WebKit/Source/core/workers/WorkerBackingThread.h

Index: third_party/WebKit/Source/core/workers/WorkerBackingThread.h
diff --git a/third_party/WebKit/Source/core/workers/WorkerBackingThread.h b/third_party/WebKit/Source/core/workers/WorkerBackingThread.h
index 08b3fc25ce26f869ab93a104a7ae986c12c4a57d..afbc4a0509ac1bdcb64a2d2d4975bd60f1734183 100644
--- a/third_party/WebKit/Source/core/workers/WorkerBackingThread.h
+++ b/third_party/WebKit/Source/core/workers/WorkerBackingThread.h
@@ -61,6 +61,9 @@ public:
 
     v8::Isolate* isolate() { return m_isolate; }
 
+    static void MemoryPressureNotificationToWorkerThreadIsolates(
+        v8::MemoryPressureLevel);
+
 private:
     WorkerBackingThread(const char* name, bool shouldCallGCOnShutdown);
     WorkerBackingThread(WebThread*, bool shouldCallGCOnSHutdown);