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

ppapi/cpp/media_stream_video_track.h

 // 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.
 
 #ifndef PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_
 #define PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_
 
 #include <string>
 
 #include "ppapi/c/ppb_media_stream_video_track.h"
@@ skipping 55 matching lines @@
   /// @endcode
   ///
   /// @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 A <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(const int32_t attributes[],
                     const CompletionCallback& callback);
 
   /// Gets attribute value for a given attribute name.
   ///
   /// @param[in] attrib A <code>PP_MediaStreamVideoTrack_Attrib</code> for
   /// querying.
   /// @param[out] value A int32_t for storing the attribute value.
   ///
   /// @return An int32_t containing a result code from <code>pp_errors.h</code>.
@@ skipping 48 matching lines @@
   ///
   /// @param[in] resource A <code>Resource</code> to test.
   ///
   /// @return True if <code>resource</code> is a MediaStream video track.
   static bool IsMediaStreamVideoTrack(const Resource& resource);
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_MEDIA_STREAM_VIDEO_TRACK_H_