Fix native api in preparation for native_api example.

Add native api conversions for video frames and video renderer. This
also requires some changes to sdk/BUILD to avoid cyclic dependencies.

Bug: webrtc:8832
Change-Id: Ibf21e63bdcae195dcb61d63f9262e6a8dc4fa790
Reviewed-on: https://webrtc-review.googlesource.com/57142
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22340}

sdk/objc/Framework/Native/api/video_renderer.mm

@@ -0,0 +1,23 @@
+/*
+ *  Copyright 2018 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.
+ */
+
+#include "sdk/objc/Framework/Native/api/video_renderer.h"
+
+#include "rtc_base/ptr_util.h"
+#include "sdk/objc/Framework/Native/src/objc_video_renderer.h"
+
+namespace webrtc {
+
+std::unique_ptr<rtc::VideoSinkInterface<VideoFrame>> ObjCToNativeVideoRenderer(
+    id<RTCVideoRenderer> objc_video_renderer) {
+  return rtc::MakeUnique<ObjCVideoRenderer>(objc_video_renderer);
+}
+
+}  // namespace webrtc