[Oilpan] Add a GC_PLUGIN_IGNORE with a TODO comment

Source/web/WebDevToolsFrontendImpl.h

Index: Source/web/WebDevToolsFrontendImpl.h
diff --git a/Source/web/WebDevToolsFrontendImpl.h b/Source/web/WebDevToolsFrontendImpl.h
index 83de9fd35ea2b6a70b08d69c887deeeaf646c3a4..72ad49f27da5445a275891747895a4c740151166 100644
--- a/Source/web/WebDevToolsFrontendImpl.h
+++ b/Source/web/WebDevToolsFrontendImpl.h
@@ -62,7 +62,7 @@ public:
     void setInjectedScriptForOrigin(const String& origin, const String& source) override;
 
 private:
-    WebLocalFrameImpl* m_webFrame;
+    RawPtrWillBeWeakPersistent<WebLocalFrameImpl> m_webFrame;

[haraken, 2015/08/27 09:13:49]

This pointer looks nasty...

- We shouldn't use WeakPersistent for a pointer that doesn't have a weak
semantics (m_webFrame is a strong back pointer to the LocalFrameImpl). Thus we
shouldn't use a WeakPersistent here.

- It is not easy to move WebDevToolsFrontendImpl to the heap and use Member,
because the WebDevToolsFrontendImpl is passed over to the chromium side.

- In the first place, it's not clear to me why the raw m_webFrame pointer is
safe. How is it guaranteed that the raw pointer doesn't become stale?

     WebDevToolsFrontendClient* m_client;
     RefPtrWillBePersistent<DevToolsHost> m_devtoolsHost;
     typedef HashMap<String, String> InjectedScriptForOriginMap;