Convert LooperExecutorTest in AppRTC Demo into JUnit test

webrtc/examples/androidapp/src/org/appspot/apprtc/util/LooperExecutor.java

Index: webrtc/examples/androidapp/src/org/appspot/apprtc/util/LooperExecutor.java
diff --git a/webrtc/examples/androidapp/src/org/appspot/apprtc/util/LooperExecutor.java b/webrtc/examples/androidapp/src/org/appspot/apprtc/util/LooperExecutor.java
index 731630405a0d1f279ae76e32935cd8e6ce96d8d5..bcc8fd1a0fc59ffed0951d289f44400cadbf63b9 100644
--- a/webrtc/examples/androidapp/src/org/appspot/apprtc/util/LooperExecutor.java
+++ b/webrtc/examples/androidapp/src/org/appspot/apprtc/util/LooperExecutor.java
@@ -71,7 +71,7 @@ public class LooperExecutor extends Thread implements Executor {
     handler.post(new Runnable() {
       @Override
       public void run() {
-        Looper.myLooper().quit();
+        handler.getLooper().quit();
         Log.d(TAG, "Looper thread finished.");
       }
     });
@@ -130,4 +130,10 @@ public class LooperExecutor extends Thread implements Executor {
     }
   }
 
+  /**
+   * Access to the handler for testing purposes.
+   */
+  Handler getHandler() {
+    return handler;
+  }
 }