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..12a354f9af4a50a89452c4752566e19203df5208 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrame.h
+++ b/third_party/WebKit/Source/core/frame/LocalFrame.h
@@ -40,6 +40,7 @@
 #include "platform/graphics/ImageOrientation.h"
 #include "platform/heap/Handle.h"
 #include "platform/scroll/ScrollTypes.h"
+#include "public/platform/BlameContext.h"
 #include "wtf/HashSet.h"
 
 namespace blink {
@@ -314,6 +315,17 @@ private:
     Member<LocalFrame> m_frame;
 };
 
+class ScopedFrameBlamer {

[tkent, 2016/06/01 23:14:56]

Please add a comment that what this class does concretely.
I couldn't guess what's "FrameBlamer" without reading the design doc.

[Xiaocheng, 2016/06/02 03:17:19]

Done.

+    WTF_MAKE_NONCOPYABLE(ScopedFrameBlamer);
+    STACK_ALLOCATED();
+public:
+    explicit ScopedFrameBlamer(LocalFrame*);

[Sami, 2016/06/01 11:05:17]

Could the parameter be const?

[Xiaocheng, 2016/06/02 03:17:19]

Yes. Done.

+    ~ScopedFrameBlamer();
+
+private:
+    BlameContext* m_frameBlameContext;

[tkent, 2016/06/01 23:14:56]

Is it safe to hold a raw pointer? Can the BlameContext object die during a
ScopedFrameBlamer is alive?

[Xiaocheng, 2016/06/02 03:17:19]

FrameBlameContext (the BlameContext subclass for frames) objects are created and
owned (*) by content::RenderFrameImpls. I guess a RenderFrameImpl won't get
deleted as long as the corresponding LocalFrame is alive, right?

So it seems that we need to make sure |frame| is alive during the lifetime of a
ScopedFrameBlamer, which means we need to store |frame| as a
|Member<LocalFrame>| here. But the overhead maybe be too big since
ScopedFrameBlamer is supposed to be a helper class for tracing that may appear
anywhere.

(*) In the current implementation, FrameBlameContext objects never get deleted.
It's a memory leak that needs to be fixed. It also means we don't need to worry
about the lifetime of |m_frameBlameContext| before the fix...

+};
+
 } // namespace blink
 
 #endif // LocalFrame_h