Have SearchProvider look up the omnibox start margin directly.

chrome/browser/ui/search/instant_controller.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_SEARCH_INSTANT_CONTROLLER_H_
 #define CHROME_BROWSER_UI_SEARCH_INSTANT_CONTROLLER_H_
 
 #include <list>
 #include <string>
 #include <utility>
@@ skipping 15 matching lines @@
 
 class BrowserInstantController;
 class InstantService;
 class InstantTab;
 class Profile;
 
 namespace content {
 class WebContents;
 }
 
+namespace gfx {
+class Rect;
+}
+
 // Macro used for logging debug events. |message| should be a std::string.
 #define LOG_INSTANT_DEBUG_EVENT(controller, message) \
     controller->LogDebugEvent(message)
 
 // InstantController drives Chrome Instant, i.e., the browser implementation of
 // the Embedded Search API (see http://dev.chromium.org/embeddedsearch).
 //
 // In extended mode, InstantController maintains and coordinates an InstantTab
 // instance of InstantPage. An InstantTab instance points to the currently
 // active tab, if it supports the Embedded Search API. InstantTab is backed by a
@@ skipping 40 matching lines @@
   void LogDebugEvent(const std::string& info) const;
 
   // Resets list of debug events.
   void ClearDebugEvents();
 
   // See comments for |debug_events_| below.
   const std::list<std::pair<int64, std::string> >& debug_events() {
     return debug_events_;
   }
 
+  // Gets the stored start-edge margin and width of the omnibox.
+  const gfx::Rect omnibox_bounds() {
+    return omnibox_bounds_;
+  }
+
   // Used by BrowserInstantController to notify InstantController about the
   // instant support change event for the active web contents.
   void InstantSupportChanged(InstantSupportState instant_support);
 
  protected:
   // Accessors are made protected for testing purposes.
   virtual InstantTab* instant_tab() const;
 
   virtual Profile* profile() const;
 
@@ skipping 105 matching lines @@
   // its suggestions with the omnibox.
   gfx::Rect omnibox_bounds_;
 
   // List of events and their timestamps, useful in debugging Instant behaviour.
   mutable std::list<std::pair<int64, std::string> > debug_events_;
 
   DISALLOW_COPY_AND_ASSIGN(InstantController);
 };
 
 #endif  // CHROME_BROWSER_UI_SEARCH_INSTANT_CONTROLLER_H_