Add option to enable ECDSA key for Java API.

Review URL: https://codereview.webrtc.org/1312293003

Cr-Commit-Position: refs/heads/master@{#9835}

webrtc/examples/androidapp/src/org/appspot/apprtc/PeerConnectionClient.java

@@ -421,6 +421,8 @@ public class PeerConnectionClient {
     rtcConfig.tcpCandidatePolicy = PeerConnection.TcpCandidatePolicy.DISABLED;
     rtcConfig.bundlePolicy = PeerConnection.BundlePolicy.MAXBUNDLE;
     rtcConfig.rtcpMuxPolicy = PeerConnection.RtcpMuxPolicy.REQUIRE;
+    // Use ECDSA encryption.
+    rtcConfig.keyType = PeerConnection.KeyType.ECDSA;
 
     peerConnection = factory.createPeerConnection(
         rtcConfig, pcConstraints, pcObserver);