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

ppapi/api/ppb_media_stream_video_track.idl

Index: ppapi/api/ppb_media_stream_video_track.idl
diff --git a/ppapi/api/ppb_media_stream_video_track.idl b/ppapi/api/ppb_media_stream_video_track.idl
index 1f331c0596aac00296c4c3d7687b0e9af68842a0..70d14db42bc21e58dcb73db0a240ef19671514fb 100644
--- a/ppapi/api/ppb_media_stream_video_track.idl
+++ b/ppapi/api/ppb_media_stream_video_track.idl
@@ -32,11 +32,15 @@ enum PP_MediaStreamVideoTrack_Attrib {
    * 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.
    */
   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),
+   * 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).
    */
@@ -44,6 +48,9 @@ enum PP_MediaStreamVideoTrack_Attrib {
 
   /**
    * 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),
+   * 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).
    */
@@ -51,7 +58,10 @@ enum PP_MediaStreamVideoTrack_Attrib {
 
   /**
    * 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
 };
@@ -95,6 +105,9 @@ interface PPB_MediaStreamVideoTrack {
    * 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,