Make ImportedStyleSheetClient GarbageCollected

third_party/WebKit/Source/core/css/StyleRuleImport.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2005, 2006, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 20 matching lines @@
 namespace blink {
 
 StyleRuleImport* StyleRuleImport::create(const String& href, MediaQuerySet* media)
 {
     return new StyleRuleImport(href, media);
 }
 
 StyleRuleImport::StyleRuleImport(const String& href, MediaQuerySet* media)
     : StyleRuleBase(Import)
     , m_parentStyleSheet(nullptr)
-    , m_styleSheetClient(this)
+    , m_styleSheetClient(new ImportedStyleSheetClient(this))
     , m_strHref(href)
     , m_mediaQueries(media)
     , m_loading(false)
 {
     if (!m_mediaQueries)
         m_mediaQueries = MediaQuerySet::create(String());
 
     ThreadState::current()->registerPreFinalizer(this);
 }
 
 StyleRuleImport::~StyleRuleImport()
 {
 }
 
 void StyleRuleImport::dispose()
 {
     if (m_resource)
-        m_resource->removeClient(&m_styleSheetClient);
+        m_resource->removeClient(m_styleSheetClient);

[haraken, 2016/05/20 09:21:10]

Can you move this to a pre-finalizer of ImportedStyleSheetClient? (Then you can
remove a pre-finalizer from StyleRuleImport.)

The model is to let all resource clients remove itself from the owner resource
in their pre-finalizers (If the client inherits from ResourceOwner, the client
doesn't need to have a pre-finalizer).

[yhirano, 2016/05/23 11:29:05]

In this case StyleRuleImport has the resource and calls |addClient|, so it looks
natural to me that StyleRuleImport is responsible for removing the client from
the resource. It is possible to access the resource from the client
(m_owner->m_resource), but is it better than the current code?

     m_resource = nullptr;
 }
 
 DEFINE_TRACE_AFTER_DISPATCH(StyleRuleImport)
 {
     visitor->trace(m_styleSheetClient);
     visitor->trace(m_parentStyleSheet);
     visitor->trace(m_mediaQueries);
     visitor->trace(m_styleSheet);
     visitor->trace(m_resource);
@@ skipping 63 matching lines @@
 
     FetchRequest request(ResourceRequest(absURL), FetchInitiatorTypeNames::css, m_parentStyleSheet->charset());
     m_resource = CSSStyleSheetResource::fetch(request, fetcher);
     if (m_resource) {
         // if the import rule is issued dynamically, the sheet may be
         // removed from the pending sheet count, so let the doc know
         // the sheet being imported is pending.
         if (m_parentStyleSheet && m_parentStyleSheet->loadCompleted() && rootSheet == m_parentStyleSheet)
             m_parentStyleSheet->startLoadingDynamicSheet();
         m_loading = true;
-        m_resource->addClient(&m_styleSheetClient);
+        m_resource->addClient(m_styleSheetClient);
     }
 }
 
 } // namespace blink