Remove calls of PrerenderTracker::TryCancel in ChromeResourceDispatcherHostDelegate::HandleExternal…

chrome/browser/chromeos/external_protocol_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/chromeos/external_protocol_dialog.h"
 
 #include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/external_protocol/external_protocol_handler.h"
@@ skipping 17 matching lines @@
 }  // namespace
 
 ///////////////////////////////////////////////////////////////////////////////
 // ExternalProtocolHandler
 
 // static
 void ExternalProtocolHandler::RunExternalProtocolDialog(
     const GURL& url, int render_process_host_id, int routing_id) {
   WebContents* web_contents = tab_util::GetWebContentsByID(
       render_process_host_id, routing_id);
-  DCHECK(web_contents);

[tburkard, 2014/01/06 10:54:38]

Why this change, seems like the semantics of |web_contents| hasn't changed by
the change in the other file.

I guess this may have been a race condition in the old code already that you are
fixing now?

[jam, 2014/01/06 15:44:18]

I actually had to change this to fix a crash, so the semantics changed. The
prerendering check on the IO thread must have masked this case. On all other
platforms though, web_contents is NULL tested.

   new ExternalProtocolDialog(web_contents, url);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // ExternalProtocolDialog
 
 ExternalProtocolDialog::~ExternalProtocolDialog() {
 }
 
 //////////////////////////////////////////////////////////////////////////////
@@ skipping 60 matching lines @@
 
   gfx::NativeWindow parent_window;
   if (web_contents) {
     parent_window = web_contents->GetView()->GetTopLevelNativeWindow();
   } else {
     // Dialog is top level if we don't have a web_contents associated with us.
     parent_window = NULL;
   }
   views::DialogDelegate::CreateDialogWidget(this, NULL, parent_window)->Show();
 }