Enable pp::flash::FontFile support on Windows

ppapi/cpp/private/flash_font_file.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 PPAPI_CPP_PRIVATE_FLASH_FONT_FILE_H_
 #define PPAPI_CPP_PRIVATE_FLASH_FONT_FILE_H_
 
 #include "ppapi/c/private/pp_private_font_charset.h"
 #include "ppapi/cpp/resource.h"
 
@@ skipping 10 matching lines @@
   // Default constructor for making an is_null() FontFile resource.
   FontFile();
   FontFile(const InstanceHandle& instance,
            const PP_BrowserFont_Trusted_Description* description,
            PP_PrivateFontCharset charset);
   virtual ~FontFile();
 
   // Returns true if the required interface is available.
   static bool IsAvailable();
 
+  // Returns true if this interface is supported for Windows.
+  bool IsSupportedForWindows();
+
   bool GetFontTable(uint32_t table, void* output, uint32_t* output_length);
 };
 
 }  // namespace flash
 }  // namespace pp
 
 #endif  // PPAPI_CPP_PRIVATE_FLASH_FONT_FILE_H_