Let AssociatedURLLoader listen to destruction of the Document used for loading

third_party/WebKit/Source/web/AssociatedURLLoader.h

Index: third_party/WebKit/Source/web/AssociatedURLLoader.h
diff --git a/third_party/WebKit/Source/web/AssociatedURLLoader.h b/third_party/WebKit/Source/web/AssociatedURLLoader.h
index 4f22667855cf4999bb79e569a1d85b6fbfec67a1..eb884dbc866a7d9fe6d1e990fa231c3a3e5e513f 100644
--- a/third_party/WebKit/Source/web/AssociatedURLLoader.h
+++ b/third_party/WebKit/Source/web/AssociatedURLLoader.h
@@ -57,15 +57,26 @@ public:
     void setDefersLoading(bool) override;
     void setLoadingTaskRunner(blink::WebTaskRunner*) override;
 
-private:
+    // Called by |m_observer| to handle destruction of the Document associated
+    // with the frame given to the constructor.
+    void documentDestroyed();
+    void disposeObserver();
 
+private:
     class ClientAdapter;
+    class Observer;
 
-    Persistent<WebLocalFrameImpl> m_frameImpl;
-    WebURLLoaderOptions m_options;
     WebURLLoaderClient* m_client;
+    WebURLLoaderOptions m_options;
+
+    // An adapter which converts the DocumentThreadableLoaderClient method
+    // calls into the WebURLLoaderClient method calls.
     OwnPtr<ClientAdapter> m_clientAdapter;
     OwnPtr<DocumentThreadableLoader> m_loader;
+
+    // A ContextLifecycleObserver for cancelling |m_loader| when the Document
+    // is detached.
+    Persistent<Observer> m_observer;
 };
 
 } // namespace blink