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

chrome/browser/chromeos/external_protocol_dialog.cc

Index: chrome/browser/chromeos/external_protocol_dialog.cc
===================================================================
--- chrome/browser/chromeos/external_protocol_dialog.cc	(revision 243063)
+++ chrome/browser/chromeos/external_protocol_dialog.cc	(working copy)
@@ -35,7 +35,6 @@
     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);
 }