Don't wait to close tabs waiting for JavaScript dialogs.

content/browser/web_contents/web_contents_impl.h

Index: content/browser/web_contents/web_contents_impl.h
diff --git a/content/browser/web_contents/web_contents_impl.h b/content/browser/web_contents/web_contents_impl.h
index 7b0429de7aa84e4f648b0ec4c4a686fe11e8b93f..a79dff3fffca57087c49a51dc1964f3145004e18 100644
--- a/content/browser/web_contents/web_contents_impl.h
+++ b/content/browser/web_contents/web_contents_impl.h
@@ -466,6 +466,7 @@ class CONTENT_EXPORT WebContentsImpl
   void RunBeforeUnloadConfirm(RenderFrameHost* render_frame_host,
                               bool is_reload,
                               IPC::Message* reply_msg) override;
+  bool IsJavaScriptDialogShowing() const override;
   void RunFileChooser(RenderFrameHost* render_frame_host,
                       const FileChooserParams& params) override;
   void DidAccessInitialDocument() override;
@@ -1295,6 +1296,9 @@ class CONTENT_EXPORT WebContentsImpl
   // delegate of this WebContentsImpl is nulled before its destructor is called.
   JavaScriptDialogManager* dialog_manager_;
 
+  // Set to true when there is an active JavaScript dialog showing.
+  bool is_showing_javascript_dialog_ = false;
+
   // Set to true when there is an active "before unload" dialog.  When true,
   // we've forced the throbber to start in Navigate, and we need to remember to
   // turn it off in OnJavaScriptMessageBoxClosed if the navigation is canceled.