Revert "Add Alpha Channel Support For WebRTC Unity Plugin"

This reverts commit 7ed2af5b461387191de2456cba906dd5d25766b6.

Reason for revert: breaking buildbot

Original change's description:
> 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}

TBR=magjed@webrtc.org,gyzhou@chromium.org,qiangchen@chromium.org

Change-Id: I6994d7e87170f97216886a747548a988ca71b7d0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:8645
Reviewed-on: https://webrtc-review.googlesource.com/35420
Reviewed-by: Lu Liu <lliuu@webrtc.org>
Commit-Queue: Lu Liu <lliuu@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21396}
diff --git a/examples/unityplugin/unity_plugin_apis.cc b/examples/unityplugin/unity_plugin_apis.cc
index 34c28d9..ae98a83 100644
--- a/examples/unityplugin/unity_plugin_apis.cc
+++ b/examples/unityplugin/unity_plugin_apis.cc
@@ -24,13 +24,12 @@
 int CreatePeerConnection(const char** turn_urls,
                          const int no_of_urls,
                          const char* username,
-                         const char* credential,
-                         bool mandatory_receive_video) {
+                         const char* credential) {
   g_peer_connection_map[g_peer_connection_id] =
       new rtc::RefCountedObject<SimplePeerConnection>();
 
   if (!g_peer_connection_map[g_peer_connection_id]->InitializePeerConnection(
-          turn_urls, no_of_urls, username, credential, mandatory_receive_video))
+          turn_urls, no_of_urls, username, credential, false))
     return -1;
 
   return g_peer_connection_id++;