Oilpan: Prepare to move AXObjectCache to the heap

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 2186 matching lines @@
 Document& Document::axObjectCacheOwner() const
 {
     Document& top = topDocument();
     if (top.frame() && top.frame()->pagePopupOwner()) {
         ASSERT(!top.m_axObjectCache);
         return top.frame()->pagePopupOwner()->document().axObjectCacheOwner();
     }
     return top;
 }
 
 void Document::clearAXObjectCache()

[haraken, 2015/04/28 10:45:21]

It is unsafe to land this CL at the moment since Document's destructor is
calling clearAXObjectCache().

We need to wait for https://codereview.chromium.org/1089813004/ to land and
remove clearAXObjectCache() from the destructor. However, it's not easy to
remove it since currently Document::detach is not always called for all
Documents.

 {
     ASSERT(&axObjectCacheOwner() == this);
-    // Clear the cache member variable before calling delete because attempts
-    // are made to access it during destruction.
-    m_axObjectCache.clear();
+    // Clear the cache member variable before calling discard because attempts

[haraken, 2015/04/28 10:45:21]

What is discard?

[keishi, 2015/05/28 06:49:15]

My mistake. I got confused. Reverted.

+    // are made to access it during discard.
+    OwnPtrWillBeRawPtr<AXObjectCache> cache = m_axObjectCache.release();
+    if (cache)
+        cache->dispose();

[haraken, 2015/04/28 10:45:21]

Nit:

if (m_axObjectCache)
  m_axObjectCache->dispose();
m_axObjectCache.clear();

[keishi, 2015/05/28 06:49:15]

Done.

 }
 
 AXObjectCache* Document::existingAXObjectCache() const
 {
     // If the renderer is gone then we are in the process of destruction.
     // This method will be called before m_frame = nullptr.
     if (!axObjectCacheOwner().layoutView())
         return 0;
 
     return axObjectCacheOwner().m_axObjectCache.get();
@@ skipping 3475 matching lines @@
 #if ENABLE(OILPAN)
     visitor->trace(m_importsController);
     visitor->trace(m_docType);
     visitor->trace(m_implementation);
     visitor->trace(m_autofocusElement);
     visitor->trace(m_focusedElement);
     visitor->trace(m_hoverNode);
     visitor->trace(m_activeHoverElement);
     visitor->trace(m_documentElement);
     visitor->trace(m_titleElement);
+    visitor->trace(m_axObjectCache);
     visitor->trace(m_markers);
     visitor->trace(m_cssTarget);
     visitor->trace(m_currentScriptStack);
     visitor->trace(m_scriptRunner);
     visitor->trace(m_listsInvalidatedAtDocument);
     for (int i = 0; i < numNodeListInvalidationTypes; ++i)
         visitor->trace(m_nodeLists[i]);
     visitor->trace(m_cssCanvasElements);
     visitor->trace(m_topLayerElements);
     visitor->trace(m_elemSheet);
@@ skipping 42 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif