Add SetAudioPlayout and SetAudioRecording methods to the PeerConnection API (II)

Second attempt to land https://webrtc-review.googlesource.com/c/src/+/16180

Now removes voice_engine dependency from peerconnection and fixes a minor
const issue in NullAudioPoller.

TBR=solenberg

Bug: webrtc:7313
Change-Id: Ibfddbdc76118581e4a4dc64575203f84c1659e5c
Reviewed-on: https://webrtc-review.googlesource.com/17784
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Henrik Andreassson <henrika@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20526}

sdk/android/api/org/webrtc/PeerConnection.java

@@ -363,6 +363,18 @@ public class PeerConnection {
 
   public native void setRemoteDescription(SdpObserver observer, SessionDescription sdp);
 
+  // True if remote audio should be played out. Defaults to true.
+  // Note that even if playout is enabled, streams will only be played out if
+  // the appropriate SDP is also applied. The main purpose of this API is to
+  // be able to control the exact time when audio playout starts.
+  public native void setAudioPlayout(boolean playout);
+
+  // True if local audio shall be recorded. Defaults to true.
+  // Note that even if recording is enabled, streams will only be recorded if
+  // the appropriate SDP is also applied. The main purpose of this API is to
+  // be able to control the exact time when audio recording starts.
+  public native void setAudioRecording(boolean recording);
+
   public boolean setConfiguration(RTCConfiguration config) {
     return nativeSetConfiguration(config, nativeObserver);
   }