Reland of BWE allocation strategy

TBR=stefan@webrtc.org,alexnarest@webrtc.org

Bug: webrtc:8243
Change-Id: Ie68e4f414b2ac32ba4e64877cb250fabcb089a07
Reviewed-on: https://webrtc-review.googlesource.com/13940
Commit-Queue: Alex Narest <alexnarest@webrtc.org>
Reviewed-by: Alex Narest <alexnarest@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20369}

sdk/objc/Framework/Headers/WebRTC/RTCPeerConnection.h

@@ -24,6 +24,7 @@
 @class RTCRtpSender;
 @class RTCSessionDescription;
 @class RTCLegacyStatsReport;
+@class RTCBitrateAllocationStrategy;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -193,6 +194,13 @@ RTC_EXPORT
           currentBitrateBps:(nullable NSNumber *)currentBitrateBps
               maxBitrateBps:(nullable NSNumber *)maxBitrateBps;
 
+/** Sets current strategy. If not set default WebRTC allocator will be used.
+ *   May be changed during an active session. The strategy
+ *   ownership is passed with std::unique_ptr
+ */
+- (void)setBitrateAllocationStrategy:
+        (RTCBitrateAllocationStrategy *_Nullable)bitrateAllocationStrategy;
+
 /** Start or stop recording an Rtc EventLog. */
 - (BOOL)startRtcEventLogWithFilePath:(NSString *)filePath
                       maxSizeInBytes:(int64_t)maxSizeInBytes;