Add assertion to EmbeddedTestServer creation method

net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServer.java

Index: net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServer.java
diff --git a/net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServer.java b/net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServer.java
index cef3cccd84a2a176bbb5270dceedfe7b207590db..72f03e680dc198b0d733356e2cb05882521926ce 100644
--- a/net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServer.java
+++ b/net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServer.java
@@ -10,8 +10,11 @@ import android.content.Intent;
 import android.content.ServiceConnection;
 import android.os.Environment;
 import android.os.IBinder;
+import android.os.Looper;
 import android.os.RemoteException;
 
+import org.junit.Assert;
+
 import org.chromium.base.Log;
 
 import java.io.File;
@@ -226,6 +229,9 @@ public class EmbeddedTestServer {
      */
     public static EmbeddedTestServer createAndStartServer(Context context)
             throws InterruptedException {
+        Assert.assertNotEquals("EmbeddedTestServer should not be created on UiThread, "
+                + "the instantiation will hang forever waiting for tasks to post to UI thread",
+                Looper.getMainLooper(), Looper.myLooper());
         EmbeddedTestServer server = new EmbeddedTestServer();
         server.initializeNative(context);
         server.addDefaultHandlers("");