iOS: Add ability to specify audio constraints.

webrtc/sdk/BUILD.gn

Index: webrtc/sdk/BUILD.gn
diff --git a/webrtc/sdk/BUILD.gn b/webrtc/sdk/BUILD.gn
index 0affad03a7dd313eb2793525bd293b56ece55e91..0f6312780133ea46fc6d67a3440f4fd1261e5061 100644
--- a/webrtc/sdk/BUILD.gn
+++ b/webrtc/sdk/BUILD.gn
@@ -73,6 +73,8 @@ if (is_ios || (is_mac && mac_deployment_target == "10.7")) {
     sources = [
       "objc/Framework/Classes/RTCAVFoundationVideoSource+Private.h",
       "objc/Framework/Classes/RTCAVFoundationVideoSource.mm",
+      "objc/Framework/Classes/RTCAudioSource+Private.h",
+      "objc/Framework/Classes/RTCAudioSource.mm",
       "objc/Framework/Classes/RTCAudioTrack+Private.h",
       "objc/Framework/Classes/RTCAudioTrack.mm",
       "objc/Framework/Classes/RTCConfiguration+Private.h",
@@ -88,6 +90,8 @@ if (is_ios || (is_mac && mac_deployment_target == "10.7")) {
       "objc/Framework/Classes/RTCIceServer.mm",
       "objc/Framework/Classes/RTCMediaConstraints+Private.h",
       "objc/Framework/Classes/RTCMediaConstraints.mm",
+      "objc/Framework/Classes/RTCMediaSource+Private.h",
+      "objc/Framework/Classes/RTCMediaSource.mm",
       "objc/Framework/Classes/RTCMediaStream+Private.h",
       "objc/Framework/Classes/RTCMediaStream.mm",
       "objc/Framework/Classes/RTCMediaStreamTrack+Private.h",
@@ -130,6 +134,7 @@ if (is_ios || (is_mac && mac_deployment_target == "10.7")) {
       "objc/Framework/Classes/avfoundationvideocapturer.h",
       "objc/Framework/Classes/avfoundationvideocapturer.mm",
       "objc/Framework/Headers/WebRTC/RTCAVFoundationVideoSource.h",
+      "objc/Framework/Headers/WebRTC/RTCAudioSource.h",
       "objc/Framework/Headers/WebRTC/RTCAudioTrack.h",
       "objc/Framework/Headers/WebRTC/RTCConfiguration.h",
       "objc/Framework/Headers/WebRTC/RTCDataChannel.h",
@@ -137,6 +142,7 @@ if (is_ios || (is_mac && mac_deployment_target == "10.7")) {
       "objc/Framework/Headers/WebRTC/RTCIceCandidate.h",
       "objc/Framework/Headers/WebRTC/RTCIceServer.h",
       "objc/Framework/Headers/WebRTC/RTCMediaConstraints.h",
+      "objc/Framework/Headers/WebRTC/RTCMediaSource.h",
       "objc/Framework/Headers/WebRTC/RTCMediaStream.h",
       "objc/Framework/Headers/WebRTC/RTCMediaStreamTrack.h",
       "objc/Framework/Headers/WebRTC/RTCPeerConnection.h",