Add Alpha Channel Support For WebRTC Unity Plugin

This CL make webrtc unity plugin compatible with alpha channel support.

Bug: webrtc:8645
Change-Id: I3250aede47b31c4685e57d11fb2b2e86b824f9c4
Reviewed-on: https://webrtc-review.googlesource.com/32325
Commit-Queue: Qiang Chen <qiangchen@chromium.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: George Zhou <gyzhou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#21394}
diff --git a/examples/unityplugin/unity_plugin_apis.h b/examples/unityplugin/unity_plugin_apis.h
index 814b967..b32f9e2 100644
--- a/examples/unityplugin/unity_plugin_apis.h
+++ b/examples/unityplugin/unity_plugin_apis.h
@@ -19,9 +19,11 @@
 typedef void (*I420FRAMEREADY_CALLBACK)(const uint8_t* data_y,
                                         const uint8_t* data_u,
                                         const uint8_t* data_v,
+                                        const uint8_t* data_a,
                                         int stride_y,
                                         int stride_u,
                                         int stride_v,
+                                        int stride_a,
                                         uint32_t width,
                                         uint32_t height);
 typedef void (*LOCALDATACHANNELREADY_CALLBACK)();
@@ -47,7 +49,8 @@
 WEBRTC_PLUGIN_API int CreatePeerConnection(const char** turn_urls,
                                            const int no_of_urls,
                                            const char* username,
-                                           const char* credential);
+                                           const char* credential,
+                                           bool mandatory_receive_video);
 // Close a peerconnection.
 WEBRTC_PLUGIN_API bool ClosePeerConnection(int peer_connection_id);
 // Add a audio stream. If audio_only is true, the stream only has an audio