Attribute Stuff to Frames with FrameBlamer

third_party/WebKit/Source/core/frame/LocalFrame.h

Index: third_party/WebKit/Source/core/frame/LocalFrame.h
diff --git a/third_party/WebKit/Source/core/frame/LocalFrame.h b/third_party/WebKit/Source/core/frame/LocalFrame.h
index 2e8d5735469ca7e5e96efa5604dde3135d0a1b97..0d351e0c44982a37129f44d42b0381dd3238ffdc 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrame.h
+++ b/third_party/WebKit/Source/core/frame/LocalFrame.h
@@ -314,6 +314,30 @@ private:
     Member<LocalFrame> m_frame;
 };
 
+// A helper class for attributing cost inside a scope to a LocalFrame, with
+// output written to the trace log. The class is irrelevant to the core logic
+// of LocalFrame.  Sample usage:
+//
+// void foo(LocalFrame* frame)
+// {
+//     ScopedFrameBlamer frameBlamer(frame);
+//     TRACE_EVENT0("blink", "foo");
+//     // Do some real work...
+// }
+//
+// In Trace Viewer, we can find the cost of slice |foo| attributed to |frame|.
+// Design doc: https://docs.google.com/document/d/15BB-suCb9j-nFt55yCFJBJCGzLg2qUm3WaSOPb8APtI/edit?usp=sharing
+class ScopedFrameBlamer {
+    WTF_MAKE_NONCOPYABLE(ScopedFrameBlamer);
+    STACK_ALLOCATED();
+public:
+    explicit ScopedFrameBlamer(LocalFrame*);
+    ~ScopedFrameBlamer();
+
+private:
+    Member<LocalFrame> m_frame;
+};
+
 } // namespace blink
 
 #endif // LocalFrame_h