Omnibox: Fix OnEscapeKeyPressed Crash

The associated bug implies a crash on the line
content::WebContents* contents = controller_->GetWebContents();
if (!contents->IsLoading()) {

This crash looks similar to the crash observed in
crbug.com/12250014
where we also assumed that GetWebContents() was non-NULL.

That was fixed by
https://chromiumcodereview.appspot.com/12250014

Peter wrote:
>>>
If we're still getting reports for this crash, then I'd say let's check in and
see if it makes the reports stop.

I'd also like to know if anywhere else assumes a non-NULL WebContents.  If this
makes the crash reports stop, we should fix any other such places too.
>>>

This is one of the other places.

BUG=167510


Review URL: https://chromiumcodereview.appspot.com/12340087

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@184845 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/omnibox/omnibox_edit_model.cc

@@ -834,7 +834,7 @@ bool OmniboxEditModel::OnEscapeKeyPressed() {
   // We do not clear the pending entry from the omnibox when a load is first
   // stopped.  If the user presses Escape while stopped, we clear it.
   content::WebContents* contents = controller_->GetWebContents();
-  if (!contents->IsLoading()) {
+  if (contents && !contents->IsLoading()) {
     contents->GetController().DiscardNonCommittedEntries();
     view_->Update(NULL);
   }