some fixes and warning disables in ui/ for building on win x64

ui/gfx/text_utils.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 "ui/gfx/text_utils.h"
 
 #include "base/i18n/char_iterator.h"
 
 namespace gfx {
 
 string16 RemoveAcceleratorChar(const string16& s,
                                char16 accelerator_char,
                                int* accelerated_char_pos,
                                int* accelerated_char_span) {
   bool escaped = false;
-  int last_char_pos = -1;
+  ptrdiff_t last_char_pos = -1;
   int last_char_span = 0;
   base::i18n::UTF16CharIterator chars(&s);
   string16 accelerator_removed;
 
   accelerator_removed.reserve(s.size());
   while (!chars.end()) {
     int32 c = chars.get();
     int array_pos = chars.array_pos();
     chars.Advance();
 
@@ skipping 13 matching lines @@
 
   if (accelerated_char_pos)
     *accelerated_char_pos = last_char_pos;
   if (accelerated_char_span)
     *accelerated_char_span = last_char_span;
 
   return accelerator_removed;
 }
 
 }  // namespace gfx