Avoid memory allocation for PPB_FileIO Read when callback is blocking.

ppapi/c/ppb_file_io.h

Index: ppapi/c/ppb_file_io.h
diff --git a/ppapi/c/ppb_file_io.h b/ppapi/c/ppb_file_io.h
index fe0e1bd4bba47ad62c899bb84994b188ac03b9de..aba7a1b3a56659b5ea4be5e17b749ccbd5845b7e 100644
--- a/ppapi/c/ppb_file_io.h
+++ b/ppapi/c/ppb_file_io.h
@@ -3,7 +3,7 @@
  * found in the LICENSE file.
  */
 
-/* From ppb_file_io.idl modified Tue Jun 11 15:21:38 2013. */
+/* From ppb_file_io.idl modified Tue Oct 22 13:47:58 2013. */
 
 #ifndef PPAPI_C_PPB_FILE_IO_H_
 #define PPAPI_C_PPB_FILE_IO_H_
@@ -135,7 +135,8 @@ struct PPB_FileIO_1_1 {
    * @param[out] info The <code>PP_FileInfo</code> structure representing all
    * information about the file.
    * @param[in] callback A <code>PP_CompletionCallback</code> to be called upon
-   * completion of Query().
+   * completion of Query(). If <code>callback</code> is blocking, then
+   * <code>info</code> must remain valid until after the callback runs.
    *
    * @return An int32_t containing an error code from <code>pp_errors.h</code>.
    * PP_ERROR_FAILED will be returned if the file isn't opened, and
@@ -170,6 +171,7 @@ struct PPB_FileIO_1_1 {
    * large enough to hold the specified number of bytes to read.  This function
    * might perform a partial read, meaning all the requested bytes
    * might not be returned, even if the end of the file has not been reached.
+   * The FileIO object must have been opened with read access.
    *
    * ReadToArray() is preferred to Read() when doing asynchronous operations.
    *
@@ -180,7 +182,8 @@ struct PPB_FileIO_1_1 {
    * @param[in] bytes_to_read The number of bytes to read from
    * <code>offset</code>.
    * @param[in] callback A <code>PP_CompletionCallback</code> to be called upon
-   * completion of Read().
+   * completion of Read(). If <code>callback</code> is blocking, then
+   * <code>buffer</code> must remain valid until after the callback runs.
    *
    * @return The number of bytes read or an error code from
    * <code>pp_errors.h</code>. If the return value is 0, then end-of-file was
@@ -267,7 +270,8 @@ struct PPB_FileIO_1_1 {
   /**
    * ReadToArray() reads from an offset in the file.  A PP_ArrayOutput must be
    * provided so that output will be stored in its allocated buffer.  This
-   * function might perform a partial read.
+   * function might perform a partial read. The FileIO object must have been
+   * opened with read access.
    *
    * @param[in] file_io A <code>PP_Resource</code> corresponding to a file
    * FileIO.