Tweaks to PPB_VarArrayBuffer in preperation for taking out of Dev.

ppapi/api/dev/ppb_var_array_buffer_dev.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.
  */
 
 /**
  * This file defines the <code>PPB_VarArrayBuffer_Dev</code> struct.
  */
 
 label Chrome {
-  M17 = 0.1
+  M18 = 0.2
 };
 
 /**
  * PPB_VarArrayBuffer_Dev API. This provides a way to interact with JavaScript
  * ArrayBuffers, which represent a contiguous sequence of bytes. To manage the
  * reference count for a VarArrayBuffer, please see PPB_Var. Note that
  * these Vars are not part of the embedding page's DOM, and can only be shared
  * with JavaScript via pp::Instance's PostMessage and HandleMessage functions.
  */
 [macro="PPB_VAR_ARRAY_BUFFER_DEV_INTERFACE"]
 interface PPB_VarArrayBuffer_Dev {
   /**
    * Create a zero-initialized VarArrayBuffer.
    *
-   * @param[in] size_in_bytes The size of the array buffer that will be created.
+   * @param[in] size_in_bytes The size of the ArrayBuffer that will be created.
    *
-   * @return A PP_Var which represents an VarArrayBuffer of the requested size
+   * @return A PP_Var which represents a VarArrayBuffer of the requested size
    *         with a reference count of 1.
    */
   PP_Var Create([in] uint32_t size_in_bytes);
+
   /**
-   * Returns the length of the VarArrayBuffer in bytes.
+   * Retrieves the length of the VarArrayBuffer in bytes. On success,
+   * byte_length is set to the length of the given ArrayBuffer var. On failure,
+   * byte_length is unchanged (this could happen, for instance, if the given
+   * PP_Var is not of type PP_VARTYPE_ARRAY_BUFFER). Note that ByteLength() will
+   * successfully retrieve the the size of an ArrayBuffer even if the
+   * ArrayBuffer is not currently mapped.
    *
-   * @return The length of the VarArrayBuffer in bytes.
+   * @param[in] array The ArrayBuffer whose length should be returned.
+   *
+   * @param[out] byte_length A variable which is set to the length of the given
+   *             ArrayBuffer on success.
+   *
+   * @return PP_TRUE on success, PP_FALSE on failure.
    */
-  uint32_t ByteLength([in] PP_Var array);
+  PP_Bool ByteLength([in] PP_Var array, [out] uint32_t byte_length);
+
   /**
-   * Returns a pointer to the beginning of the buffer for the given array.
+   * Maps the ArrayBuffer in to the module's address space and returns a pointer
+   * to the beginning of the buffer for the given ArrayBuffer PP_Var. Note that
+   * calling Map() can be a relatively expensive operation. Use care when
+   * calling it in performance-critical code. For example, you should call it
+   * only once when looping over an ArrayBuffer:
    *
-   * @param[in] array The array whose buffer should be returned.
+   * <code>
+   *   char* data = (char*)(array_buffer_if.Map(array_buffer_var));
+   *   uint32_t byte_length = 0;
+   *   PP_Bool ok = array_buffer_if.ByteLength(array_buffer_var, &byte_length);
+   *   if (!ok)
+   *     return DoSomethingBecauseMyVarIsNotAnArrayBuffer();
+   *   for (uint32_t i = 0; i < byte_length; ++i)
+   *     data[i] = 'A';
+   * </code>
    *
-   * @return A pointer to the buffer for this array.
+   * @param[in] array The ArrayBuffer whose internal buffer should be returned.
+   *
+   * @return A pointer to the internal buffer for this ArrayBuffer. Returns NULL
+   *         if the given PP_Var is not of type PP_VARTYPE_ARRAY_BUFFER.
    */
   mem_t Map([in] PP_Var array);
+
+  /**
+   * Unmaps the given ArrayBuffer var from the module address space. Use this if
+   * you want to save memory but might want to Map the buffer again later. The
+   * PP_Var remains valid and should still be released using PPB_Var when you
+   * are done with the ArrayBuffer.
+   *
+   * @param[in] array The ArrayBuffer which should be released.
+   */
+  void Unmap([in] PP_Var array);
 };