Oilpan: extend tracing over WebFrame trees.

public/web/WebFrame.h

Index: public/web/WebFrame.h
diff --git a/public/web/WebFrame.h b/public/web/WebFrame.h
index 950dad8e023f6ad2e25a0f222b95800744b5e085..8debe9a1e45cd668e63c601de24d7fedab18368e 100644
--- a/public/web/WebFrame.h
+++ b/public/web/WebFrame.h
@@ -681,16 +681,22 @@ public:
 
 #if BLINK_IMPLEMENTATION
     static WebFrame* fromFrame(Frame*);
-    static void traceChildren(Visitor*, WebFrame*);
+    static void traceFrames(Visitor*, WebFrame*);
+    static void clearWeakFrames(Visitor*, WebFrame*);
 #endif
 
 protected:
-    explicit WebFrame();
+    WebFrame();
     virtual ~WebFrame();
 
 private:
     friend class OpenedFrameTracker;
 
+#if BLINK_IMPLEMENTATION
+    static void traceFrame(Visitor*, WebFrame*);
+    static bool isAlive(Visitor*, WebFrame*);
+#endif
+
     WebFrame* m_parent;
     WebFrame* m_previousSibling;
     WebFrame* m_nextSibling;