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
 // WebContents and it does not own that WebContents.
 //
 // InstantController is owned by Browser via BrowserInstantController.
 class InstantController : public InstantPage::Delegate {
  public:
   InstantController(BrowserInstantController* browser,
                     bool extended_enabled);
   virtual ~InstantController();
 
   // Sets the stored start-edge margin and width of the omnibox.
   void SetOmniboxBounds(const gfx::Rect& bounds);
 
+  // Gets the stored start-edge margin and width of the omnibox.
+  gfx::Rect GetOmniboxBounds();

[samarth, 2013/08/06 18:09:32]

Make this a simple accessor: omnibox_bounds()

[jeremycho, 2013/08/06 21:03:04]

Done.

+
   // Notifies |instant_Tab_| to toggle voice search.
   void ToggleVoiceSearch();
 
   // Called if the browser is navigating to a search URL for |search_terms| with
   // search-term-replacement enabled. If |instant_tab_| can be used to process
   // the search, this does so and returns true. Else, returns false.
   bool SubmitQuery(const string16& search_terms);
 
   // Called to indicate that the omnibox focus state changed with the given
   // |reason|. If |focus_state| is FOCUS_NONE, |view_gaining_focus| is set to
@@ skipping 150 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_