Attempt to make waitForIdleHandler reliable.

    /**

     * Block until the given handler becomes idle, or until timeoutMs has passed.

     */

    private static void waitForIdleHandler(HandlerThread handler, int timeoutMs) {

    private static void waitForIdleHandler(HandlerThread handlerThread, int timeoutMs) {

        final ConditionVariable cv = new ConditionVariable();

        final MessageQueue queue = handler.getLooper().getQueue();

        final IdleHandler idleHandler = () -> {

            synchronized (queue) {

                cv.open();

                return false; // Remove the idleHandler.

            }

        };

        synchronized (queue) {

            if (queue.isIdle()) {

                return;

            }

            queue.addIdleHandler(idleHandler);

        }

        final Handler handler = new Handler(handlerThread.getLooper());

        handler.post(() -> cv.open());

        if (!cv.block(timeoutMs)) {

            fail("HandlerThread " + handler.getName() +

            fail("HandlerThread " + handlerThread.getName() +

                    " did not become idle after " + timeoutMs + " ms");

            queue.removeIdleHandler(idleHandler);

        }

    }