[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.

[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).
    */
@@ -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),

[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).
    */
@@ -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,