AppRTCDemo(android): specify DtlsSrtpKeyAgreement:true in CreatePeerConnection's constraints.

This is required to interop with Chrome now that SDES is disabled in Chrome (as of r5640).

BUG=2774
R=jiayl@chromium.org

Review URL: https://webrtc-codereview.appspot.com/10749004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5809 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/talk/examples/android/src/org/appspot/apprtc/AppRTCDemoActivity.java b/talk/examples/android/src/org/appspot/apprtc/AppRTCDemoActivity.java
index 46b6169..7d92a36 100644
--- a/talk/examples/android/src/org/appspot/apprtc/AppRTCDemoActivity.java
+++ b/talk/examples/android/src/org/appspot/apprtc/AppRTCDemoActivity.java
@@ -179,7 +179,7 @@
   private static void createDataChannelToRegressionTestBug2302(
       PeerConnection pc) {
     DataChannel dc = pc.createDataChannel("dcLabel", new DataChannel.Init());
-    abortUnless("dcLabel".equals(dc.label()), "WTF?");
+    abortUnless("dcLabel".equals(dc.label()), "Unexpected label corruption?");
     dc.close();
     dc.dispose();
   }
@@ -189,6 +189,8 @@
     factory = new PeerConnectionFactory();
 
     MediaConstraints pcConstraints = appRtcClient.pcConstraints();
+    pcConstraints.mandatory.add(
+        new MediaConstraints.KeyValuePair("DtlsSrtpKeyAgreement", "true"));
     pcConstraints.optional.add(
         new MediaConstraints.KeyValuePair("RtpDataChannels", "true"));
     pc = factory.createPeerConnection(iceServers, pcConstraints, pcObserver);