Move |PlatformFont::GetStringWidth()| implementation up into font.cc directly.

ui/gfx/platform_font_pango.h

 // 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.
 
 #ifndef UI_GFX_PLATFORM_FONT_PANGO_H_
 #define UI_GFX_PLATFORM_FONT_PANGO_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 26 matching lines @@
   // drawn at y + height + underline_position;
   double underline_position() const;
   // The thickness to draw the underline.
   double underline_thickness() const;
 
   // Overridden from PlatformFont:
   virtual Font DeriveFont(int size_delta, int style) const OVERRIDE;
   virtual int GetHeight() const OVERRIDE;
   virtual int GetBaseline() const OVERRIDE;
   virtual int GetAverageCharacterWidth() const OVERRIDE;
-  virtual int GetStringWidth(const string16& text) const OVERRIDE;
   virtual int GetExpectedTextWidth(int length) const OVERRIDE;
   virtual int GetStyle() const OVERRIDE;
   virtual std::string GetFontName() const OVERRIDE;
   virtual int GetFontSize() const OVERRIDE;
   virtual NativeFont GetNativeFont() const OVERRIDE;
 
  private:
   // Create a new instance of this object with the specified properties. Called
   // from DeriveFont.
   PlatformFontPango(SkTypeface* typeface,
@@ skipping 45 matching lines @@
   double underline_position_pixels_;
   double underline_thickness_pixels_;
 
   // The default font, used for the default constructor.
   static Font* default_font_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PLATFORM_FONT_PANGO_H_