Add ContextLifecycleObserver::frame()

I'm replacing DOMWindowProperty with ContextLifecycleObserver.
(ContextLifecycleObserver::contextDestroyed() is called already almost at the same
timing as DOMWindowProperty::frameDestroyed().)

To make the replacement easier, this CL introduces ContextLifecycleObserver::frame().
Also this CL moves ApplicationCache to ContextLifecycleObserver.

BUG=610176

Review-Url: https://codereview.chromium.org/2562303002
Cr-Commit-Position: refs/heads/master@{#437852}

third_party/WebKit/Source/core/dom/BUILD.gn

@@ -42,6 +42,7 @@ blink_core_sources("dom") {
     "ContextFeatures.h",
     "ContextLifecycleNotifier.cpp",
     "ContextLifecycleNotifier.h",
+    "ContextLifecycleObserver.cpp",
     "ContextLifecycleObserver.h",
     "DOMArrayBuffer.cpp",
     "DOMArrayBuffer.h",

third_party/WebKit/Source/core/dom/ContextLifecycleObserver.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/dom/ContextLifecycleObserver.h"
+
+#include "core/dom/Document.h"
+#include "core/frame/LocalFrame.h"
+
+namespace blink {
+
+LocalFrame* ContextLifecycleObserver::frame() const {
+  return getExecutionContext() && getExecutionContext()->isDocument()
+             ? toDocument(getExecutionContext())->frame()
+             : nullptr;
+}
+}

third_party/WebKit/Source/core/dom/ContextLifecycleObserver.h

@@ -33,11 +33,18 @@
 
 namespace blink {
 
+class LocalFrame;
+
 class CORE_EXPORT ContextLifecycleObserver
     : public LifecycleObserver<ExecutionContext, ContextLifecycleObserver> {
  public:
+  // Returns null after the observing context is detached.
   ExecutionContext* getExecutionContext() const { return lifecycleContext(); }
 
+  // Returns null after the observing context is detached or if the context
+  // doesn't have a frame (i.e., if the context is not a Document).
+  LocalFrame* frame() const;
+
   enum Type {
     GenericType,
     SuspendableObjectType,

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

@@ -39,7 +39,7 @@
 namespace blink {
 
 ApplicationCache::ApplicationCache(LocalFrame* frame)
-    : DOMWindowProperty(frame) {
+    : ContextLifecycleObserver(frame->document()) {
   ApplicationCacheHost* cacheHost = applicationCacheHost();
   if (cacheHost)
     cacheHost->setApplicationCache(this);
@@ -47,13 +47,12 @@ ApplicationCache::ApplicationCache(LocalFrame* frame)
 
 DEFINE_TRACE(ApplicationCache) {
   EventTargetWithInlineData::trace(visitor);
-  DOMWindowProperty::trace(visitor);
+  ContextLifecycleObserver::trace(visitor);
 }
 
-void ApplicationCache::frameDestroyed() {
+void ApplicationCache::contextDestroyed() {
   if (ApplicationCacheHost* cacheHost = applicationCacheHost())
     cacheHost->setApplicationCache(0);
-  DOMWindowProperty::frameDestroyed();
 }
 
 ApplicationCacheHost* ApplicationCache::applicationCacheHost() const {

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

@@ -26,9 +26,8 @@
 #ifndef ApplicationCache_h
 #define ApplicationCache_h
 
+#include "core/dom/ContextLifecycleObserver.h"
 #include "core/events/EventTarget.h"
-
-#include "core/frame/DOMWindowProperty.h"
 #include "core/loader/appcache/ApplicationCacheHost.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
@@ -39,7 +38,7 @@ class ExceptionState;
 class LocalFrame;
 
 class ApplicationCache final : public EventTargetWithInlineData,
-                               public DOMWindowProperty {
+                               public ContextLifecycleObserver {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(ApplicationCache);
 
@@ -49,7 +48,7 @@ class ApplicationCache final : public EventTargetWithInlineData,
   }
   ~ApplicationCache() override {}
 
-  void frameDestroyed() override;
+  void contextDestroyed() override;
 
   unsigned short status() const;
   void update(ExceptionState&);