Have SearchProvider look up the omnibox start margin directly.

chrome/browser/ui/omnibox/omnibox_edit_controller.h

Index: chrome/browser/ui/omnibox/omnibox_edit_controller.h
diff --git a/chrome/browser/ui/omnibox/omnibox_edit_controller.h b/chrome/browser/ui/omnibox/omnibox_edit_controller.h
index 582550003fe8b051f1a4f069f69f6a1de5ba0f9f..b6517398353dffe5dda0100a4035d6a54cd54503 100644
--- a/chrome/browser/ui/omnibox/omnibox_edit_controller.h
+++ b/chrome/browser/ui/omnibox/omnibox_edit_controller.h
@@ -18,7 +18,6 @@ class WebContents;
 
 namespace gfx {
 class Image;
-class Rect;
 }
 
 // I am in hack-and-slash mode right now.
@@ -70,9 +69,6 @@ class OmniboxEditController {
   // Returns the WebContents of the currently active tab.
   virtual content::WebContents* GetWebContents() const = 0;
 
-  // Returns the bounds for the omnibox.
-  virtual gfx::Rect GetOmniboxBounds() const = 0;
-
  protected:
   virtual ~OmniboxEditController() {}
 };