Don't leave renderer process frozen when canceling JavaScript dialogs.

chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h

Index: chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h
diff --git a/chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h b/chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h
index 38153fc9e5785f1c7ff69f7ad6c79f7ffb46f8df..f7038d993be4efa452dd2705c7d37879544f2517 100644
--- a/chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h
+++ b/chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h
@@ -12,6 +12,7 @@
 #include "base/time/time.h"
 #include "chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h"
 #include "content/public/browser/javascript_dialog_manager.h"
+#include "content/public/browser/web_contents_observer.h"
 
 // Extra data for JavaScript dialogs to add Chrome-only features.
 class ChromeJavaScriptDialogExtraData {
@@ -27,7 +28,9 @@ class ChromeJavaScriptDialogExtraData {
 
 // A controller + model class for JavaScript alert, confirm, prompt, and
 // onbeforeunload dialog boxes.
-class JavaScriptAppModalDialog : public AppModalDialog {
+class JavaScriptAppModalDialog
+    : public AppModalDialog,
+      public content::WebContentsObserver {
  public:
   typedef std::map<void*, ChromeJavaScriptDialogExtraData> ExtraDataMap;
 
@@ -49,6 +52,10 @@ class JavaScriptAppModalDialog : public AppModalDialog {
   virtual bool IsJavaScriptModalDialog() OVERRIDE;
   virtual void Invalidate() OVERRIDE;
 
+  // Overridden from content::WebContentsObserver:
+  virtual void RenderViewDeleted(
+      content::RenderViewHost* render_view_host) OVERRIDE;
+
   // Callbacks from NativeDialog when the user accepts or cancels the dialog.
   void OnCancel(bool suppress_js_messages);
   void OnAccept(const string16& prompt_text, bool suppress_js_messages);
@@ -76,6 +83,9 @@ class JavaScriptAppModalDialog : public AppModalDialog {
   void NotifyDelegate(bool success, const string16& prompt_text,
                       bool suppress_js_messages);
 
+  // Which RenderViewHost requested the dialog and will run |callback_|.
+  content::RenderViewHost* render_view_host_;
+
   // A map of extra Chrome-only data associated with the delegate_.
   // Can be inspected via extra_data_map_[web_contents_].
   ExtraDataMap* extra_data_map_;