Add utility method for WebString to base::FilePath conversion

third_party/WebKit/Source/platform/blink_platform.gyp

 #
 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 45 matching lines @@
       '<(DEPTH)/skia/skia.gyp:skia',
     ],
     'defines': [
       'BLINK_COMMON_IMPLEMENTATION=1',
       'INSIDE_BLINK',
     ],
     'include_dirs': [
       '<(SHARED_INTERMEDIATE_DIR)/blink',
     ],
     'sources': [
+      'exported/FilePathConversion.cpp',
       'exported/URLConversion.cpp',
       'exported/WebCString.cpp',
       'exported/WebCommon.cpp',
       'exported/WebString.cpp',
     ],
   },
   {
     'target_name': 'blink_heap_asm_stubs',
     'type': 'static_library',
     # VS2010 does not correctly incrementally link obj files generated
@@ skipping 346 matching lines @@
           ['OS=="android"', {
             'cflags!': ['-mthumb'],
           }],
         ],
       },{  # target_arch!="arm"
         'type': 'none',
       }],
     ],
   }],
 }