Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/page/Page.cpp

Index: Source/core/page/Page.cpp
diff --git a/Source/core/page/Page.cpp b/Source/core/page/Page.cpp
index 800c4df63e33508f716888d8774f8044b80fbf67..8693aeea570fa13f1fe0dba6c634a15433cd4976 100644
--- a/Source/core/page/Page.cpp
+++ b/Source/core/page/Page.cpp
@@ -53,6 +53,7 @@
 #include "core/rendering/FastTextAutosizer.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/TextAutosizer.h"
+#include "core/speech/SpeechInput.h"
 #include "core/storage/StorageNamespace.h"
 #include "platform/plugins/PluginData.h"
 #include "wtf/HashMap.h"
@@ -470,8 +471,8 @@ void Page::settingsChanged(SettingsDelegate::ChangeType changeType)
             frame->document()->initDNSPrefetch();
         break;
     case SettingsDelegate::MultisamplingChange: {
-        HashSet<MultisamplingChangedObserver*>::iterator stop = m_multisamplingChangedObservers.end();
-        for (HashSet<MultisamplingChangedObserver*>::iterator it = m_multisamplingChangedObservers.begin(); it != stop; ++it)
+        WillBePersistentHeapHashSet<RawPtrWillBeWeakMember<MultisamplingChangedObserver> >::iterator stop = m_multisamplingChangedObservers.end();
+        for (WillBePersistentHeapHashSet<RawPtrWillBeWeakMember<MultisamplingChangedObserver> >::iterator it = m_multisamplingChangedObservers.begin(); it != stop; ++it)
             (*it)->multisamplingChanged(m_settings->openGLMultisamplingEnabled());
         break;
     }
@@ -539,9 +540,18 @@ PassOwnPtr<LifecycleNotifier<Page> > Page::createLifecycleNotifier()
 
 void Page::trace(Visitor* visitor)
 {
+    visitor->registerWeakMembers<Page, &Page::clearWeakMembers>(this);

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

Instead of making Page hold a weak reference to the Page itself, how about
making SpeechInput hold the weak reference to the Page? Then you don't need to
redirect the weak processing in Page::clearWeakMembers.

Also this change looks not directly related to the TreeScope change (but is
needed for the TreeScope change). You might want to land this part ahead of
time.

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

The Page does not hold a weak reference to itself. The Page is registering with
the garbage collector that it wants a weak callback during garbage collection.
When SpeechInput is moved to the heap we can move the weak callback where it
belongs. However, SpeechInput is a supplement so in order to move it we have to
move all the page supplements to the heap. That is a separate change. Once that
is done we can clean this up. :)

This is related to this change in the sense that it was not needed before this
change. The problem is that the SpeechInput would have to go through its
document to get to the page. Both document and page can now be dead in the
destructor of SpeechInput and we need to use weak processing.

+    visitor->trace(m_multisamplingChangedObservers);
     Supplementable<Page>::trace(visitor);
 }
 
+void Page::clearWeakMembers(Visitor* visitor)
+{
+    SpeechInput* input = SpeechInput::from(this);
+    if (input)
+        input->clearWeakMembers(visitor);
+}
+
 void Page::willBeDestroyed()
 {
     // Disable all agents prior to resetting the frame view.