Update/move RTCVideoRendererAdapter to webrtc/api/objc.

webrtc/api/BUILD.gn

 # Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../build/webrtc.gni")
 
@@ skipping 18 matching lines @@
     sources = [
       "objc/RTCI420Frame+Private.h",
       "objc/RTCI420Frame.h",
       "objc/RTCI420Frame.mm",
       "objc/RTCIceServer+Private.h",
       "objc/RTCIceServer.h",
       "objc/RTCIceServer.mm",
       "objc/RTCOpenGLVideoRenderer.h",
       "objc/RTCOpenGLVideoRenderer.mm",
       "objc/RTCVideoRenderer.h",
+      "objc/RTCVideoRendererAdapter.h",
+      "objc/RTCVideoRendererAdapter.mm",
       "objc/WebRTC-Prefix.pch",
     ]
 
     if (is_ios) {
       sources += [
         "objc/RTCEAGLVideoView.h",
         "objc/RTCEAGLVideoView.m",
       ]
     }
 
     if (is_mac) {
       sources += [
         "objc/RTCNSGLVideoView.h",
         "objc/RTCNSGLVideoView.m",
       ]
     }
   }
 }