Make the file chooser use PP_ArrayOutput

ppapi/api/pp_array_output.idl

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 /**
  * PP_ArrayOutput_GetDataBuffer is a callback function to allocate plugin
  * memory for an array. It returns the allocated memory or null on failure.
  *
  * This function will be called reentrantly. This means that if you call a
@@ skipping 57 matching lines @@
  *   }
  *   return output->data;
  * }
  * void MyFunction() {
  *   MyArrayOutput array = { NULL, 0 };
  *   PP_ArrayOutput output = { &MyGetDataBuffer, &array };
  *   ppb_foo->GetData(&output);
  * }
  * @endcode
  */
+[passByValue]
 struct PP_ArrayOutput {
   /**
    * A pointer to the allocation function that the browser implements.
    */
   PP_ArrayOutput_GetDataBuffer GetDataBuffer;
 
   /**
    * Data that is passed to the allocation function. Typically, this is used
    * to communicate how the data should be stored.
    */
   mem_t user_data;
 };