Fix a Windows crash bug with javascript alerts from extension popups.

chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h

Index: chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h
diff --git a/chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h b/chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h
index aa70d58d9f1f74668b88c4474c5995052bc32580..fb84f5cff727888dcd917ca60111ebbd025348b6 100644
--- a/chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h
+++ b/chrome/browser/ui/app_modal_dialogs/app_modal_dialog.h
@@ -82,6 +82,9 @@ class AppModalDialog {
 
   content::WebContents* web_contents_;
 
+  // True if CompleteDialog was called.
+  bool completed_;
+
   DISALLOW_COPY_AND_ASSIGN(AppModalDialog);
 };