ApprtDemo Android: Switch between front and back camera.

This adds a UI icon for switching between the front and back camera.
This cl adds the possibility to change between the front and back camera while in a call
or before the other end have connected.

BUG=3786
R=glaznev@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/23219004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7553 4adac7df-926f-26a2-2b94-8c16560cd09d

talk/examples/android/src/org/appspot/apprtc/AppRTCDemoActivity.java

@@ -139,6 +139,14 @@ public class AppRTCDemoActivity extends Activity
           }
         });
 
+    ((ImageButton) findViewById(R.id.button_switch_camera)).setOnClickListener(
+        new View.OnClickListener() {
+          @Override
+          public void onClick(View view) {
+            pc.switchCamera();
+          }
+        });
+
     ((ImageButton) findViewById(R.id.button_toggle_debug)).setOnClickListener(
         new View.OnClickListener() {
           @Override