[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 0 is specified, the default value will be used.

[yzshen1, 2014/02/18 18:11:40]

(Have you considered this?) An alternative is to reset all the fields every time
Configure() is called, those fields that are not listed will be reset to default
value. For example:
- first Configure call: { WIDTH = 100; HEIGHT = 100; FORMAT = RGBA }
- second Configure call: { FORMAT = RGBA } (width and height will be reset to
default values)

[Peng, 2014/02/18 22:30:09]

I considered it. I think your suggestion and current implementation are both OK.
I don't have any preference. Because it has been implemented in this way, so I
did not change it.

Which one do you think it is better?

    */
   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 with the video source (webcam),

[yzshen1, 2014/02/18 18:11:40]

nit: "different from"?

[Peng, 2014/02/18 22:30:09]

Done.

+   * frames will be scaled to specified size. If 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 with the video source (webcam),

[yzshen1, 2014/02/18 18:11:40]

ditto

[Peng, 2014/02/18 22:30:09]

Done.

+   * frames will be scaled to specified size. If 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
+   * with the video source (webcam), frames will be converted to specified
+   * format. If <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.
    *
@@ skipping 23 matching lines @@
    * @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>.
    */
   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.
@@ skipping 76 matching lines @@
   /**
    * 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);
 };