diff -r 000000000000 -r 6474c204b198 build/mobile/robocop/RobocopUtils.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/build/mobile/robocop/RobocopUtils.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko;
+
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.TimeUnit;
+
+import android.app.Activity;
+
+public final class RobocopUtils {
+    private static final int MAX_WAIT_MS = 20000;
+
+    private RobocopUtils() {}
+
+    public static void runOnUiThreadSync(Activity activity, final Runnable runnable) {
+        final SynchronousQueue syncQueue = new SynchronousQueue();
+        activity.runOnUiThread(
+            new Runnable() {
+                public void run() {
+                    runnable.run();
+                    try {
+                        syncQueue.put(new Object());
+                    } catch (InterruptedException e) {
+                        FennecNativeDriver.log(FennecNativeDriver.LogLevel.ERROR, e);
+                    }
+                }
+            });
+        try {
+            // Wait for the UiThread code to finish running
+            if (syncQueue.poll(MAX_WAIT_MS, TimeUnit.MILLISECONDS) == null) {
+                FennecNativeDriver.log(FennecNativeDriver.LogLevel.ERROR,
+                                       "time-out waiting for UI thread");
+                FennecNativeDriver.logAllStackTraces(FennecNativeDriver.LogLevel.ERROR);
+            }
+        } catch (InterruptedException e) {
+            FennecNativeDriver.log(FennecNativeDriver.LogLevel.ERROR, e);
+        }
+    }
+}