Add a keyboard shortcut on Escape that emits the IDC_STOP command....

chrome/browser/autocomplete/autocomplete_edit_view_mac.mm

 // Copyright (c) 2009 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/autocomplete/autocomplete_edit_view_mac.h"
 
 #include <Carbon/Carbon.h>  // kVK_Return
 
 #include "app/clipboard/clipboard.h"
 #include "app/resource_bundle.h"
@@ skipping 582 matching lines @@
     model_->OnUpOrDownKeyPressed(model_->result().size());
     return true;
   }
 
   if (cmd == @selector(scrollPageUp:)) {
     model_->OnUpOrDownKeyPressed(-model_->result().size());
     return true;
   }
 
   if (cmd == @selector(cancelOperation:)) {
-    model_->OnEscapeKeyPressed();
-    return true;
+    return model_->OnEscapeKeyPressed();
   }
 
   if (cmd == @selector(insertTab:)) {
     if (model_->is_keyword_hint() && !model_->keyword().empty()) {
       model_->AcceptKeyword();
       return true;
     }
   }
 
   // TODO(shess): Option-tab, would normally insert a literal tab
@@ skipping 191 matching lines @@
     clipboard->ReadBookmark(NULL, &url_str);
     // pass resulting url string through GURL to normalize
     GURL url(url_str);
     if (url.is_valid()) {
       return UTF8ToWide(url.spec());
     }
   }
 
   return std::wstring();
 }