Reland ObjC API for BWE allocation strategy

Bug: webrtc:8243
Change-Id: Ib1b8349bffe98490ba5f1d12b18e848e89cdb9ce
Reviewed-on: https://webrtc-review.googlesource.com/16640
Reviewed-by: Alex Narest <alexnarest@webrtc.org>
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20534}

sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnection+Native.h

@@ -0,0 +1,34 @@
+/*
+ *  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 "WebRTC/RTCPeerConnection.h"
+
+#include <memory>
+
+namespace rtc {
+class BitrateAllocationStrategy;
+}  // namespace rtc
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * This class extension exposes methods that work directly with injectable C++ components.
+ */
+@interface RTCPeerConnection ()
+
+/** Sets current strategy. If not set default WebRTC allocator will be used. May be changed during
+ *  an active session.
+ */
+- (void)setBitrateAllocationStrategy:
+        (std::unique_ptr<rtc::BitrateAllocationStrategy>)bitrateAllocationStrategy;
+
+@end
+
+NS_ASSUME_NONNULL_END