Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/html/imports/HTMLImportChild.h

Index: Source/core/html/imports/HTMLImportChild.h
diff --git a/Source/core/html/imports/HTMLImportChild.h b/Source/core/html/imports/HTMLImportChild.h
index f87d9feebf0dd9299160db02459aece60cd77f53..776ca59621c956d439f0b0822df3fd53c7454730 100644
--- a/Source/core/html/imports/HTMLImportChild.h
+++ b/Source/core/html/imports/HTMLImportChild.h
@@ -34,6 +34,7 @@
 #include "core/fetch/RawResource.h"
 #include "core/fetch/ResourceOwner.h"
 #include "core/html/imports/HTMLImport.h"
+#include "heap/Handle.h"
 #include "platform/weborigin/KURL.h"
 #include "wtf/Vector.h"
 
@@ -96,7 +97,11 @@ private:
     void shareLoader(HTMLImportChild*);
     void ensureLoader();
 
+#if ENABLE(OILPAN)
+    Persistent<Document> m_master;

[haraken, 2014/04/24 04:18:43]

Won't this cause a cycle? You are replacing a RawPtr with a Persistent.

Probably you can keep this as a raw pointer and clear it when ~Document() calls
m_importsController->wasDetachedFrom(*this).

[Mads Ager (chromium), 2014/04/24 10:57:36]

This will be no worse than it was before. The HTMLImportChild increments the
Document guardRef in its constructor and decrements it in the destructor. The
persistent here has the same effect. The Document cannot die until the
ImportChild is dead. We should indeed get rid of the persistent in a followup
change and it should be a traced member.

+#else
     Document& m_master;
+#endif
     KURL m_url;
     CustomElementMicrotaskImportStep* m_customElementMicrotaskStep;
     HTMLImportLoader* m_loader;