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

chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/app_modal_dialogs/javascript_app_modal_dialog.h"
 
 #include "base/command_line.h"
 #include "chrome/browser/browser_shutdown.h"
 #include "chrome/browser/ui/app_modal_dialogs/native_app_modal_dialog.h"
 #include "chrome/common/chrome_switches.h"
@@ skipping 85 matching lines @@
 #endif  // defined(USE_AURA)
 
   return NativeAppModalDialog::CreateNativeJavaScriptPrompt(this,
                                                             parent_window);
 }
 
 bool JavaScriptAppModalDialog::IsJavaScriptModalDialog() {
   return true;
 }
 
 void JavaScriptAppModalDialog::Invalidate() {

[Avi (use Gerrit), 2013/09/25 04:28:40]

It seems like at the end of JavaScriptAppModalDialog::NotifyDelegate, below, it
calls this function, so would the callback then happen twice?

What I would do is at both invocations of callback_ (here on line 111 and at
line 164) do:

if (!callback_.is_null()) {
  callback_.Run(/*...*/);
  callback_.Reset();
}

[Charlie Reis, 2013/09/25 16:48:34]

Not quite.  NotifyDelegate calls AppModalDialog::Invalidate (which only sets
valid_ to false), not JavaScriptAppModalDialog::Invalidate.  However, I like
your suggestion-- it's safer in general.
Done.

   if (!IsValid())
     return;
 
   AppModalDialog::Invalidate();
-  callback_.Reset();
+  callback_.Run(false, string16());
   if (native_dialog())
     CloseModalDialog();
 }
 
 void JavaScriptAppModalDialog::OnCancel(bool suppress_js_messages) {
   // If we are shutting down and this is an onbeforeunload dialog, cancel the
   // shutdown.
   // TODO(sammc): Remove this when kEnableBatchedShutdown becomes mandatory.
   if (is_before_unload_dialog_ &&
       !CommandLine::ForCurrentProcess()->HasSwitch(
@@ skipping 48 matching lines @@
   if (extra_data != extra_data_map_->end()) {
     extra_data->second.last_javascript_message_dismissal_ =
         base::TimeTicks::Now();
     extra_data->second.suppress_javascript_messages_ = suppress_js_messages;
   }
 
   // On Views, we can end up coming through this code path twice :(.
   // See crbug.com/63732.
   AppModalDialog::Invalidate();
 }