Add RequestOSFileHandle as a private PPAPI

ppapi/c/trusted/ppb_file_io_trusted.h

Index: ppapi/c/trusted/ppb_file_io_trusted.h
diff --git a/ppapi/c/trusted/ppb_file_io_trusted.h b/ppapi/c/trusted/ppb_file_io_trusted.h
index 53953fbd8b57939d9617eaa02bd7cd5ae471cf33..8e05589eeb621c09b7a89d6ad67efbf72ce07a0b 100644
--- a/ppapi/c/trusted/ppb_file_io_trusted.h
+++ b/ppapi/c/trusted/ppb_file_io_trusted.h
@@ -3,7 +3,7 @@
  * found in the LICENSE file.
  */
 
-/* From trusted/ppb_file_io_trusted.idl modified Wed Oct  5 14:06:02 2011. */
+/* From trusted/ppb_file_io_trusted.idl modified Wed Mar 27 14:50:12 2013. */
 
 #ifndef PPAPI_C_TRUSTED_PPB_FILE_IO_TRUSTED_H_
 #define PPAPI_C_TRUSTED_PPB_FILE_IO_TRUSTED_H_
@@ -35,6 +35,8 @@ struct PPB_FileIOTrusted_0_4 {
    * descriptor. The FileIO object must have been opened with a successful
    * call to FileIO::Open.  The file descriptor will be closed automatically
    * when the FileIO object is closed or destroyed.
+   *
+   * TODO(hamaji): Remove this and use RequestOSFileHandle instead.
    */
   int32_t (*GetOSFileDescriptor)(PP_Resource file_io);
   /**