Remove hidden dependency on HandlerThread

    private static class ImsExecutorFactory implements ExecutorFactory {

        private final HandlerThread mThreadHandler;

        private final Handler mHandler;

        public ImsExecutorFactory() {

            mThreadHandler = new HandlerThread("ImsHandlerThread");

            mThreadHandler.start();

            mHandler = new Handler(mThreadHandler.getLooper());

        }

        @Override

        public void executeRunnable(Runnable runnable) {

            mThreadHandler.getThreadHandler().post(runnable);

            mHandler.post(runnable);

        }

    }