Make ApplicationCache a DOMWindowClient

ApplicationCache is a per-DOMWindow thing instead of a per-ExecutionContext thing.
It should use DOMWindowClient instead of ContextClient.

BUG=610176

Review-Url: https://codereview.chromium.org/2631653002
Cr-Commit-Position: refs/heads/master@{#443541}

third_party/WebKit/Source/core/loader/appcache/ApplicationCache.cpp

@@ -38,8 +38,7 @@
 
 namespace blink {
 
-ApplicationCache::ApplicationCache(LocalFrame* frame)
-    : ContextLifecycleObserver(frame->document()) {
+ApplicationCache::ApplicationCache(LocalFrame* frame) : DOMWindowClient(frame) {
   ApplicationCacheHost* cacheHost = applicationCacheHost();
   if (cacheHost)
     cacheHost->setApplicationCache(this);
@@ -47,12 +46,7 @@ ApplicationCache::ApplicationCache(LocalFrame* frame)
 
 DEFINE_TRACE(ApplicationCache) {
   EventTargetWithInlineData::trace(visitor);
-  ContextLifecycleObserver::trace(visitor);
-}
-
-void ApplicationCache::contextDestroyed() {
-  if (ApplicationCacheHost* cacheHost = applicationCacheHost())
-    cacheHost->setApplicationCache(0);
+  DOMWindowClient::trace(visitor);
 }
 
 ApplicationCacheHost* ApplicationCache::applicationCacheHost() const {
@@ -98,9 +92,7 @@ const AtomicString& ApplicationCache::interfaceName() const {
 }
 
 ExecutionContext* ApplicationCache::getExecutionContext() const {
-  if (frame())
-    return frame()->document();
-  return 0;
+  return frame() ? frame()->document() : nullptr;
 }
 
 const AtomicString& ApplicationCache::toEventType(

third_party/WebKit/Source/core/loader/appcache/ApplicationCache.h

@@ -38,7 +38,7 @@ class ExceptionState;
 class LocalFrame;
 
 class ApplicationCache final : public EventTargetWithInlineData,
-                               public ContextLifecycleObserver {
+                               public DOMWindowClient {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(ApplicationCache);
 
@@ -48,8 +48,6 @@ class ApplicationCache final : public EventTargetWithInlineData,
   }
   ~ApplicationCache() override {}
 
-  void contextDestroyed() override;
-
   unsigned short status() const;
   void update(ExceptionState&);
   void swapCache(ExceptionState&);

third_party/WebKit/Source/core/loader/appcache/ApplicationCacheHost.cpp

@@ -260,11 +260,12 @@ void ApplicationCacheHost::dispatchDOMEvent(
     const String& errorURL,
     int errorStatus,
     const String& errorMessage) {
-  if (!m_domApplicationCache)
+  // Don't dispatch an event if the window is detached.
+  if (!m_domApplicationCache || !m_domApplicationCache->domWindow())
     return;
 
   const AtomicString& eventType = ApplicationCache::toEventType(id);
-  if (eventType.isEmpty() || !m_domApplicationCache->getExecutionContext())
+  if (eventType.isEmpty())
     return;
   Event* event = nullptr;
   if (id == kProgressEvent) {