ui: Cleanup class/struct forward declarations

ui/gfx/platform_font_linux.h

 // 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.
 
 #ifndef UI_GFX_PLATFORM_FONT_LINUX_H_
 #define UI_GFX_PLATFORM_FONT_LINUX_H_
 
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "third_party/skia/include/core/SkRefCnt.h"
 #include "ui/gfx/font_render_params.h"
 #include "ui/gfx/platform_font.h"
 
 class SkTypeface;
-class SkPaint;
 
 namespace gfx {
 
 class GFX_EXPORT PlatformFontLinux : public PlatformFont {
  public:
   // TODO(derat): Get rid of the default constructor in favor of using
   // FontList (which also has the concept of a default font but may contain
   // multiple font families) everywhere. See http://crbug.com/398885#c16.
   PlatformFontLinux();
   PlatformFontLinux(const std::string& font_name, int font_size_pixels);
@@ skipping 75 matching lines @@
   // A font description string of the format used by FontList.
   static std::string* default_font_description_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PlatformFontLinux);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PLATFORM_FONT_LINUX_H_