Improve omnibox accessibility on Windows.

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

 // Copyright (c) 2011 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 373 matching lines @@
     return true;
   const NSRange all_range = NSMakeRange(0, GetTextLength());
   return NSEqualRanges(all_range, GetSelectedRange());
 }
 
 bool OmniboxViewMac::DeleteAtEndPressed() {
   return delete_at_end_pressed_;
 }
 
 void OmniboxViewMac::GetSelectionBounds(string16::size_type* start,
-                                        string16::size_type* end) {
+                                        string16::size_type* end) const {
   if (![field_ currentEditor]) {
     *start = *end = 0;
     return;
   }
 
   const NSRange selected_range = GetSelectedRange();
   *start = static_cast<size_t>(selected_range.location);
   *end = static_cast<size_t>(NSMaxRange(selected_range));
 }
 
@@ skipping 716 matching lines @@
 
 void OmniboxViewMac::PlaceCaretAt(NSUInteger pos) {
   DCHECK(pos <= GetTextLength());
   SetSelectedRange(NSMakeRange(pos, pos));
 }
 
 bool OmniboxViewMac::IsCaretAtEnd() const {
   const NSRange selection = GetSelectedRange();
   return selection.length == 0 && selection.location == GetTextLength();
 }