Add NSString category for providing iOS6-style string drawing APIs.

ui/gfx/platform_font_ios.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 "ui/gfx/platform_font_ios.h"
 
 #import <UIKit/UIKit.h>
 
 #include <cmath>
 
 #include "base/basictypes.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "ui/gfx/font.h"
 #include "ui/gfx/font_render_params.h"
+#include "ui/ios/NSString+CrStringDrawing.h"
 
 namespace gfx {
 
 ////////////////////////////////////////////////////////////////////////////////
 // PlatformFontIOS, public:
 
 PlatformFontIOS::PlatformFontIOS() {
   font_size_ = [UIFont systemFontSize];
   style_ = gfx::Font::NORMAL;
   UIFont* system_font = [UIFont systemFontOfSize:font_size_];
@@ skipping 79 matching lines @@
   font_size_ = font_size;
   style_ = style;
   CalculateMetrics();
 }
 
 void PlatformFontIOS::CalculateMetrics() {
   UIFont* font = GetNativeFont();
   height_ = font.lineHeight;
   ascent_ = font.ascender;
   cap_height_ = font.capHeight;
-  if (font) {
-    NSDictionary* attributes = @{ NSFontAttributeName : font };
-    average_width_ = std::ceil([@"x" sizeWithAttributes:attributes].width);
-  } else {
-    average_width_ = 0;
-  }
+  average_width_ = [@"x" cr_sizeWithFont:font].width;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // PlatformFont, public:
 
 // static
 PlatformFont* PlatformFont::CreateDefault() {
   return new PlatformFontIOS;
 }
 
 // static
 PlatformFont* PlatformFont::CreateFromNativeFont(NativeFont native_font) {
   return new PlatformFontIOS(native_font);
 }
 
 // static
 PlatformFont* PlatformFont::CreateFromNameAndSize(const std::string& font_name,
                                                   int font_size) {
   return new PlatformFontIOS(font_name, font_size);
 }
 
 }  // namespace gfx