Have SearchProvider look up the omnibox start margin directly.

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

 // Copyright 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/location_bar_view_mac.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
 #include "base/prefs/pref_service.h"
@@ skipping 339 matching lines @@
     if (page_action_decorations_[i]->IsVisible())
       ++result;
   }
   return result;
 }
 
 WebContents* LocationBarViewMac::GetWebContents() const {
   return browser_->tab_strip_model()->GetActiveWebContents();
 }
 
-gfx::Rect LocationBarViewMac::GetOmniboxBounds() const {
-  return gfx::Rect(NSRectToCGRect([field_ frame]));
-}
-
 PageActionDecoration* LocationBarViewMac::GetPageActionDecoration(
     ExtensionAction* page_action) {
   DCHECK(page_action);
   for (size_t i = 0; i < page_action_decorations_.size(); ++i) {
     if (page_action_decorations_[i]->page_action() == page_action)
       return page_action_decorations_[i];
   }
   // If |page_action| is the browser action of an extension, no element in
   // |page_action_decorations_| will match.
   NOTREACHED();
@@ skipping 343 matching lines @@
   WebContents* web_contents = GetWebContents();
   if (!web_contents)
     return;
 
   zoom_decoration_->Update(ZoomController::FromWebContents(web_contents));
 }
 
 void LocationBarViewMac::UpdateStarDecorationVisibility() {
   star_decoration_->SetVisible(IsStarEnabled());
 }