Introduce V8GCController::collectAllGarbage

Source/bindings/core/v8/V8GCController.h

 /*
  * Copyright (C) 2009 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 29 matching lines @@
 
 class Node;
 
 class CORE_EXPORT V8GCController {
     STATIC_ONLY(V8GCController);
 public:
     static void gcPrologue(v8::GCType, v8::GCCallbackFlags);
     static void gcEpilogue(v8::GCType, v8::GCCallbackFlags);
 
     static void collectGarbage(v8::Isolate*);
+    // You should use collectAllGarbageForTesting() when you want to collect all
+    // V8 & Blink objects. It runs multiple V8 GCs to collect references
+    // that cross the binding boundary. collectAllGarbage() also runs multipe
+    // Oilpan GCs to collect a chain of persistent handles.
+    static void collectAllGarbageForTesting(v8::Isolate*);
 
     static Node* opaqueRootForGC(v8::Isolate*, Node*);
 
     static void reportDOMMemoryUsageToV8(v8::Isolate*);
 
     static void traceDOMWrappers(v8::Isolate*, Visitor*);
 };
 
 }
 
 #endif // V8GCController_h