Omnibox: When backspacing out of keyword mode, don't highlight anything.

chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.mm

 // Copyright (c) 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/cocoa/omnibox/omnibox_view_mac.h"
 
 #include <Carbon/Carbon.h>  // kVK_Return
 
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
@@ skipping 251 matching lines @@
     // it cannot occur and DCHECK appropriately.
     [[field_ currentEditor] setSelectedRange:range];
   }
 }
 
 void OmniboxViewMac::SetWindowTextAndCaretPos(const string16& text,
                                               size_t caret_pos,
                                               bool update_popup,
                                               bool notify_text_changed) {
   DCHECK_LE(caret_pos, text.size());
-  SetTextAndSelectedRange(text, NSMakeRange(caret_pos, caret_pos));
+  SetTextAndSelectedRange(text, NSMakeRange(caret_pos, 0));
 
   if (update_popup)
     UpdatePopup();
 
   if (notify_text_changed)
     TextChanged();
 }
 
 void OmniboxViewMac::SetForcedQuery() {
   // We need to do this first, else |SetSelectedRange()| won't work.
@@ skipping 723 matching lines @@
 NSUInteger OmniboxViewMac::GetTextLength() const {
   return ([field_ currentEditor] ?
           [[[field_ currentEditor] string] length] :
           [[field_ stringValue] length]) - suggest_text_length_;
 }
 
 bool OmniboxViewMac::IsCaretAtEnd() const {
   const NSRange selection = GetSelectedRange();
   return selection.length == 0 && selection.location == GetTextLength();
 }