Enabled pressing TAB to cycle through the Omnibox results.

chrome/browser/autocomplete/autocomplete_popup_view_mac.mm

 // Copyright (c) 2010 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 <cmath>
 
 #include "chrome/browser/autocomplete/autocomplete_popup_view_mac.h"
 
 #include "base/stl_util-inl.h"
 #include "base/sys_string_conversions.h"
@@ skipping 525 matching lines @@
   if (!force_background) {
     disposition =
         event_utils::WindowOpenDispositionFromNSEvent([NSApp currentEvent]);
   }
 
   // OpenURL() may close the popup, which will clear the result set
   // and, by extension, |match| and its contents.  So copy the
   // relevant strings out to make sure they stay alive until the call
   // completes.
   const AutocompleteMatch& match = model_->result().match_at(row);
+  string16 keyword;
+  if (match.has_keyword_hint())
+    keyword.assign(match.keyword);
+
   const GURL url(match.destination_url);
-  string16 keyword;
-  const bool is_keyword_hint = model_->GetKeywordForMatch(match, &keyword);
   edit_view_->OpenURL(url, disposition, match.transition, GURL(), row,
-                      is_keyword_hint ? string16() : keyword);
+                      keyword);
 }
 
 void AutocompletePopupViewMac::UserPressedOptIn(bool opt_in) {
   PromoCounter* counter = model_->profile()->GetInstantPromoCounter();
   DCHECK(counter);
   counter->Hide();
   if (opt_in) {
     browser::ShowInstantConfirmDialogIfNecessary([field_ window],
                                                  model_->profile());
   }
@@ skipping 262 matching lines @@
                        bottomRightCornerRadius:kPopupRoundingRadius];
 
   // Draw the matrix clipped to our border.
   [NSGraphicsContext saveGraphicsState];
   [path addClip];
   [super drawRect:rect];
   [NSGraphicsContext restoreGraphicsState];
 }
 
 @end