Support using VP9 video codec in AppRTCDemo.

- Add peer connection Java API to initialize field trial string.
- Add setting option to select VP8 or Vp9 as default video codec.
- Minor code clean up and allowing 720p portrait encoding.

R=wzh@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/39899004

Cr-Commit-Position: refs/heads/master@{#8303}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8303 4adac7df-926f-26a2-2b94-8c16560cd09d

talk/examples/androidtests/src/org/appspot/apprtc/test/PeerConnectionClientTest.java

@@ -99,7 +99,7 @@ public class PeerConnectionClientTest extends InstrumentationTestCase
     }
 
     public synchronized int getWidth() { return width; }
-    public synchronized int getHeight() { return width; }
+    public synchronized int getHeight() { return height; }
     public synchronized boolean setSizeCalledBeforeRenderFrame() {
       return setSizeCalledBeforeRenderFrame;
     }
@@ -232,7 +232,7 @@ public class PeerConnectionClientTest extends InstrumentationTestCase
 
     PeerConnectionClient client = new PeerConnectionClient();
     client.createPeerConnectionFactory(
-        getInstrumentation().getContext(), true, null, this);
+        getInstrumentation().getContext(), "VP8", true, null, this);
     client.createPeerConnection(
         localRenderer, remoteRenderer, signalingParameters, 1000);
     client.createOffer();