Revert "Simple Default ObjC video codec factories."

This reverts commit 30915a742d86df55ac5c04501c0e8104675a612e.

Reason for revert: Breaks downstream.

Original change's description:
> Simple Default ObjC video codec factories.
> 
> Move the simple video encoder/decoder factory from AppRTCMobile into the
> public API so users who don't have special requirements for video codecs
> can easily get started.
> 
> Also clean up the API a little.
> 
> This CL replaces the more flexible default factories in
> https://webrtc-review.googlesource.com/c/src/+/7741 and clients that
> want to implement their own codecs will have to supply their own
> encoder/decoder factories as well. The benefits of the approach in
> this CL are a simpler API and less effects on the rest of the code.
> 
> Bug: None
> Change-Id: I4ed94090d778b4fc38b49864de1d4de4ff125d6a
> Reviewed-on: https://webrtc-review.googlesource.com/15141
> Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
> Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
> Commit-Queue: Anders Carlsson <andersc@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#20441}

TBR=magjed@webrtc.org,andersc@webrtc.org,kthelgason@webrtc.org

Change-Id: I3d4395cc9667e6c6cdb33a3b0f5c5fb5bfde9028
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: None
Reviewed-on: https://webrtc-review.googlesource.com/15182
Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
Commit-Queue: Oskar Sundbom <ossu@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20446}
diff --git a/examples/objc/AppRTCMobile/ARDVideoDecoderFactory.h b/examples/objc/AppRTCMobile/ARDVideoDecoderFactory.h
new file mode 100644
index 0000000..bc8be99
--- /dev/null
+++ b/examples/objc/AppRTCMobile/ARDVideoDecoderFactory.h
@@ -0,0 +1,16 @@
+/*
+ *  Copyright 2017 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 <Foundation/Foundation.h>
+#import "WebRTC/RTCVideoCodecFactory.h"
+
+@interface ARDVideoDecoderFactory : NSObject<RTCVideoDecoderFactory>
+
+@end