[PPAPI][MediaStream] Support configure for video input.

ppapi/api/ppb_media_stream_video_track.idl

 /* Copyright 2014 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.
  */
 
 /**
  * Defines the <code>PPB_MediaStreamVideoTrack</code> interface. Used for
  * receiving video frames from a MediaStream video track in the browser.
  * This interface is still in development (Dev API status) and may change.
  */
@@ skipping 14 matching lines @@
    */
   PP_MEDIASTREAMVIDEOTRACK_ATTRIB_NONE = 0,
 
   /**
    * The maximum number of frames to hold in the input buffer.
    * Note: this is only used as advisory; the browser may allocate more or fewer
    * based on available resources. How many frames to buffer depends on usage -
    * request at least 2 to make sure latency doesn't cause lost frames. If
    * the plugin expects to hold on to more than one frame at a time (e.g. to do
    * multi-frame processing), it should request that many more.
+   * If this attribute is not specified or value 0 is specified for this
+   * attribute, the default value will be used.
    */
   PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES = 1,
 
   /**
    * The width of video frames in pixels. It should be a multiple of 4.
+   * If the specified size is different from the video source (webcam),
+   * frames will be scaled to specified size.
+   * If this attribute is not specified or value 0 is specified, the original
+   * frame size of the video track will be used.
    *
    * Maximum value: 4096 (4K resolution).
    */
   PP_MEDIASTREAMVIDEOTRACK_ATTRIB_WIDTH = 2,
 
   /**
    * The height of video frames in pixels. It should be a multiple of 4.
+   * If the specified size is different from the video source (webcam),
+   * frames will be scaled to specified size.
+   * If this attribute is not specified or value 0 is specified, the original
+   * frame size of the video track will be used.
    *
    * Maximum value: 4096 (4K resolution).
    */
   PP_MEDIASTREAMVIDEOTRACK_ATTRIB_HEIGHT = 3,
 
   /**
    * The format of video frames. The attribute value is
-   * a <code>PP_VideoFrame_Format</code>.
+   * a <code>PP_VideoFrame_Format</code>. If the specified format is different
+   * from the video source (webcam), frames will be converted to specified
+   * format.
+   * If this attribute is not specified or value
+   * <code>PP_VIDEOFRAME_FORMAT_UNKNOWN</code> is specified, the orignal frame
+   * format of the video track will be used.
    */
   PP_MEDIASTREAMVIDEOTRACK_ATTRIB_FORMAT = 4
 };
 
 interface PPB_MediaStreamVideoTrack {
   /**
    * Determines if a resource is a MediaStream video track resource.
    *
    * @param[in] resource The <code>PP_Resource</code> to test.
    *
    * @return A <code>PP_Bool</code> with <code>PP_TRUE</code> if the given
    * resource is a Mediastream video track resource or <code>PP_FALSE</code>
    * otherwise.
    */
   PP_Bool IsMediaStreamVideoTrack([in] PP_Resource resource);
 
   /**
    * Configures underlying frame buffers for incoming frames.
    * If the application doesn't want to drop frames, then the
    * <code>PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES</code> should be
    * chosen such that inter-frame processing time variability won't overrun the
    * input buffer. If the buffer is overfilled, then frames will be dropped.
    * The application can detect this by examining the timestamp on returned
-   * frames. If <code>Configure()</code> is not called, default settings will be
-   * used.
+   * frames. If some attributes are not specified, default values will be used
+   * for those unspecified attributes. If <code>Configure()</code> is not
+   * called, default settings will be used.
    * Example usage from plugin code:
    * @code
    * int32_t attribs[] = {
    *     PP_MEDIASTREAMVIDEOTRACK_ATTRIB_BUFFERED_FRAMES, 4,
    *     PP_MEDIASTREAMVIDEOTRACK_ATTRIB_NONE};
    * track_if->Configure(track, attribs, callback);
    * @endcode
    *
    * @param[in] video_track A <code>PP_Resource</code> corresponding to a video
    * resource.
    * @param[in] attrib_list A list of attribute name-value pairs in which each
    * attribute is immediately followed by the corresponding desired value.
    * The list is terminated by
    * <code>PP_MEDIASTREAMVIDEOTRACK_ATTRIB_NONE</code>.
    * @param[in] callback <code>PP_CompletionCallback</code> to be called upon
    * completion of <code>Configure()</code>.
    *
    * @return An int32_t containing a result code from <code>pp_errors.h</code>.
+   * Returns <code>PP_ERROR_INPROGRESS</code> if there is a pending call of
+   * <code>Configure()</code> or <code>GetFrame()</code>, or the plugin
+   * holds some frames which are not recycled with <code>RecycleFrame()</code>.
+   * If an error is returned, all attributes and the underlying buffer will not
+   * be changed.
    */
   int32_t Configure([in] PP_Resource video_track,
                     [in] int32_t[] attrib_list,
                     [in] PP_CompletionCallback callback);
 
   /**
    * Gets attribute value for a given attribute name.
    *
    * @param[in] video_track A <code>PP_Resource</code> corresponding to a video
    * resource.
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   /**
    * Closes the MediaStream video track and disconnects it from video source.
    * After calling <code>Close()</code>, no new frames will be received.
    *
    * @param[in] video_track A <code>PP_Resource</code> corresponding to a
    * MediaStream video track resource.
    */
   void Close([in] PP_Resource video_track);
 };