[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..199ebb27e71d2a8e27f0786812ed7fa4d9433e07 100644
--- a/ppapi/api/ppb_media_stream_video_track.idl
+++ b/ppapi/api/ppb_media_stream_video_track.idl
@@ -32,11 +32,17 @@ 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 this attribute is not specified or value 0 is specified for this

[yzshen1, 2014/02/19 17:00:56]

Why do we need to have 0 as default value? It seems better to only have one way
to do things. What do you think? (Here and below)

[Peng, 2014/02/19 19:22:36]

I think it is better to have a way to allow developer to set the default value
explicitly. Otherwise, to set a default value, developers must configure()
without specifying the attribute. It is little weird. Especially some developers
prefer to put all supported attributes in the array. (For example: If I create
an example code for this API, I would like to put all supported attributes in
the array, and add comments to describe them.). WDYT?

+   * 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).
    */
@@ -44,6 +50,10 @@ enum PP_MediaStreamVideoTrack_Attrib {
 
   /**
    * 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).
    */
@@ -51,7 +61,12 @@ 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
+   * 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
 };
@@ -75,8 +90,9 @@ interface PPB_MediaStreamVideoTrack {
    * 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[] = {
@@ -95,6 +111,11 @@ 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>.
+   * 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,