Oilpan: Move all supplements of Page, Document, and WorkerClients to the managed heap.

Source/core/testing/InternalSettings.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 25 matching lines @@
 #include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
 class Document;
 class ExceptionState;
 class LocalFrame;
 class Page;
 class Settings;
 
+#if ENABLE(OILPAN)
+class InternalSettings FINAL : public InternalSettingsGenerated, public HeapSupplement<Page> {
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(InternalSettings);
+#else
 class InternalSettings FINAL : public InternalSettingsGenerated {
+#endif
 public:
     class Backup {
     public:
         explicit Backup(Settings*);
         void restoreTo(Settings*);
 
         bool m_originalCSSExclusionsEnabled;
         bool m_originalAuthorShadowDOMForAnyElementEnabled;
         bool m_originalStyleScoped;
         bool m_originalCSP;
@@ skipping 10 matching lines @@
         bool m_originalCompositorDrivenAcceleratedScrollEnabled;
         bool m_originalLayerSquashingEnabled;
         bool m_originalPasswordGenerationDecorationEnabled;
     };
 
     static PassRefPtrWillBeRawPtr<InternalSettings> create(Page& page)
     {
         return adoptRefWillBeNoop(new InternalSettings(page));
     }
     static InternalSettings* from(Page&);
-    void hostDestroyed() { m_page = 0; }
+
+#if !ENABLE(OILPAN)
+    void hostDestroyed() { m_page = nullptr; }
+#endif
 
     virtual ~InternalSettings();
     void resetToConsistentState();
 
     void setStandardFontFamily(const AtomicString& family, const String& script, ExceptionState&);
     void setSerifFontFamily(const AtomicString& family, const String& script, ExceptionState&);
     void setSansSerifFontFamily(const AtomicString& family, const String& script, ExceptionState&);
     void setFixedFontFamily(const AtomicString& family, const String& script, ExceptionState&);
     void setCursiveFontFamily(const AtomicString& family, const String& script, ExceptionState&);
     void setFantasyFontFamily(const AtomicString& family, const String& script, ExceptionState&);
@@ skipping 21 matching lines @@
     // FIXME: The following are RuntimeEnabledFeatures and likely
     // cannot be changed after process start. These setters should
     // be removed or moved onto internals.runtimeFlags:
     void setAuthorShadowDOMForAnyElementEnabled(bool);
     void setCSSExclusionsEnabled(bool);
     void setLangAttributeAwareFormControlUIEnabled(bool);
     void setOverlayScrollbarsEnabled(bool);
     void setStyleScopedEnabled(bool);
     void setExperimentalContentSecurityPolicyFeaturesEnabled(bool);
 
-    virtual void trace(Visitor* visitor) OVERRIDE { InternalSettingsGenerated::trace(visitor); }
+    virtual void trace(Visitor*) OVERRIDE;
 
 private:
     explicit InternalSettings(Page&);
 
     Settings* settings() const;
     Page* page() const { return m_page; }
     static const char* supplementName();
 
-    Page* m_page;
+    RawPtrWillBeWeakMember<Page> m_page;

[haraken, 2014/04/30 11:18:08]

hmm, I'm not quite sure about this pointer.

- In oilpan, InternalSettings is a HeapSupplement<Page>, so the InternalSettings
and the Page should die together. Thus this should be a strong pointer. So I
think this pointer should be RawPtrWillBeMember.

- In non-oilpan, weak processing for m_page is necessary because we have
InternalSettingsWrapper (for some reason). Do you know why we need
InternalSettingsWrapper? Can't we just make InternalSettings derive
InternalSettingsGenerated and Supplement<Page>? In other words, I wonder why we
cannot write like this:

class InternalSettings : public InternalSettingsGenerated, public
WillBeHeapSupplement<Page> { ... };

[zerny-chromium, 2014/04/30 11:46:53]

That is because InternalSettingsGenerated is RefCounted and a Supplement can't
be RefCounted. Since the base is already RefCounted we can't use
RefCountedSupplement, so the wrapper class is explicitly defined for the
non-oilpan build. For the oilpan-build the issue goes away. In both cases we are
not ensured that InternalSettings lives and dies with Page because others can
have RefPtrs/Members to it.

In general, a HeapSupplement can outlive the object it is a supplement to.

[haraken, 2014/04/30 12:02:08]

Makes sense.
In what situation do we want to let a supplement object outlive the
supplementable object?

If it outlives, we also need to care about a raw pointer in HeapSupplement that
points to the supplementable object.

class X : public HeapSupplement<Document> {
  Document& m_document;  // I was assuming that this raw pointer is safe because
the Document and X die together. We have this kind of raw pointer in this CL.
};

     Backup m_backup;
 };
 
 } // namespace WebCore
 
 #endif