Have SearchProvider look up the omnibox start margin directly.

chrome/browser/ui/omnibox/omnibox_edit_model.cc

 // 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.
 
 #include "chrome/browser/ui/omnibox/omnibox_edit_model.h"
 
 #include <string>
 
 #include "base/auto_reset.h"
 #include "base/format_macros.h"
@@ skipping 477 matching lines @@
   bool keyword_is_selected = KeywordIsSelected();
   omnibox_controller_->StartAutocomplete(
       user_text_,
       cursor_position,
       current_url,
       ClassifyPage(),
       prevent_inline_autocomplete || just_deleted_text_ ||
       (has_selected_text && inline_autocomplete_text_.empty()) ||
       (paste_state_ != NONE),
       keyword_is_selected,
-      keyword_is_selected || allow_exact_keyword_match_,
-      controller_->GetOmniboxBounds().x());
+      keyword_is_selected || allow_exact_keyword_match_);
 }
 
 void OmniboxEditModel::StopAutocomplete() {
   autocomplete_controller()->Stop(true);
 }
 
 bool OmniboxEditModel::CanPasteAndGo(const string16& text) const {
   if (!view_->command_updater()->IsCommandEnabled(IDC_OPEN_CURRENT_URL))
     return false;
 
@@ skipping 781 matching lines @@
     instant->OmniboxFocusChanged(state, reason, NULL);
 
   // Update state and notify view if the omnibox has focus and the caret
   // visibility changed.
   const bool was_caret_visible = is_caret_visible();
   focus_state_ = state;
   if (focus_state_ != OMNIBOX_FOCUS_NONE &&
       is_caret_visible() != was_caret_visible)
     view_->ApplyCaretVisibility();
 }