Pepper: Add append support to FileIO.

ppapi/api/ppb_file_io.idl

Index: ppapi/api/ppb_file_io.idl
diff --git a/ppapi/api/ppb_file_io.idl b/ppapi/api/ppb_file_io.idl
index f89ba171c10bd6c73749cab9f79e6d92b924555d..2e43ec54c1c7ca7d7ffacbe3b6fbb17ac10a3008 100644
--- a/ppapi/api/ppb_file_io.idl
+++ b/ppapi/api/ppb_file_io.idl
@@ -12,7 +12,8 @@
 
 label Chrome {
   M14 = 1.0,
-  M25 = 1.1
+  M25 = 1.1,
+  M29 = 1.2
 };
 
 /**
@@ -41,14 +42,23 @@ label Chrome {
    * Requests that the file be truncated to length 0 if it exists and is a
    * regular file. <code>PP_FILEOPENFLAG_WRITE</code> must also be specified.
    */
-   PP_FILEOPENFLAG_TRUNCATE  = 1 << 3,
+  PP_FILEOPENFLAG_TRUNCATE  = 1 << 3,
 
   /**
    * Requests that the file is created when this flag is combined with
    * <code>PP_FILEOPENFLAG_CREATE</code>.  If this flag is specified, and the
    * file already exists, then the FileIO::Open() call will fail.
    */
-  PP_FILEOPENFLAG_EXCLUSIVE = 1 << 4
+  PP_FILEOPENFLAG_EXCLUSIVE = 1 << 4,
+
+ /**
+  * Requests write access to a file, but writes will always occur at the end of
+  * the file. Mututally exclusive with <code>PP_FILEOPENFLAG_WRITE</code>.
+  *
+  * This is only supported in version 1.2 (Chrome 29) and later.
+  */
+  [version=1.2]
+  PP_FILEOPENFLAG_APPEND = 1 << 5
 };