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

Source/core/testing/InternalSettings.h

Index: Source/core/testing/InternalSettings.h
diff --git a/Source/core/testing/InternalSettings.h b/Source/core/testing/InternalSettings.h
index 7886c1c26de170fd0b8b70bf8641db872e6513a1..ec7e10174f0fdad7ad4babb7183e22d706061ebb 100644
--- a/Source/core/testing/InternalSettings.h
+++ b/Source/core/testing/InternalSettings.h
@@ -43,7 +43,12 @@ 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:
@@ -74,7 +79,10 @@ public:
         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();
@@ -116,7 +124,7 @@ public:
     void setStyleScopedEnabled(bool);
     void setExperimentalContentSecurityPolicyFeaturesEnabled(bool);
 
-    virtual void trace(Visitor* visitor) OVERRIDE { InternalSettingsGenerated::trace(visitor); }
+    virtual void trace(Visitor*) OVERRIDE;
 
 private:
     explicit InternalSettings(Page&);
@@ -125,7 +133,7 @@ private:
     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;
 };