cocoa: allow omnibox decorations to become key

chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_cell.h"
 
 #include <stddef.h>
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
@@ skipping 718 matching lines @@
 }
 
 - (void)handleFocusEvent:(NSEvent*)event
                   ofView:(AutocompleteTextField*)controlView {
   if ([controlView observer]) {
     const bool controlDown = ([event modifierFlags] & NSControlKeyMask) != 0;
     [controlView observer]->OnSetFocus(controlDown);
   }
 }
 
+- (int)leadingDecorationIndex:(LocationBarDecoration*)decoration {
+  for (size_t i = 0; i < leadingDecorations_.size(); ++i)
+    if (leadingDecorations_[i] == decoration)
+      return leadingDecorations_.size() - (i + 1);
+  return -1;
+}
+
 @end
 
 @implementation AutocompleteTextFieldCell (TestingAPI)
 
 - (const std::vector<LocationBarDecoration*>&)mouseTrackingDecorations {
   return mouseTrackingDecorations_;
 }
 
 @end