Introduce FileSystemFileUtil and -Proxy to decorate base::file_util in webkit/fileapi.

webkit/fileapi/webkit_fileapi.gypi

Index: webkit/fileapi/webkit_fileapi.gypi
diff --git a/webkit/fileapi/webkit_fileapi.gypi b/webkit/fileapi/webkit_fileapi.gypi
index c082f2cda5a1614a4b23380211a1e753b2ce7e45..ba2c347aae08625d2756c66b357c0505ed2af737 100644
--- a/webkit/fileapi/webkit_fileapi.gypi
+++ b/webkit/fileapi/webkit_fileapi.gypi
@@ -19,6 +19,10 @@
         'file_system_context.h',
         'file_system_dir_url_request_job.cc',
         'file_system_dir_url_request_job.h',
+        'file_system_file_util.cc',
+        'file_system_file_util.h',
+        'file_system_file_util_proxy.cc',
+        'file_system_file_util_proxy.h',
         'file_system_operation.cc',
         'file_system_operation.h',
         'file_system_path_manager.cc',
@@ -47,4 +51,3 @@
     },
   ],
 }
-