Fix test failure due to out of UI thread runnning.

After Ie8c42d60a0bff7636795a958a475058798061fe5,
ActivityTestRule is no longer a subclass of UiThreadTestRule, and looks
like the new UiThreadTest annotation is not working for Parameterized
test. As a temporary fix, use runOnUiThread instead of @UiThreadTest.

Change-Id: I69d035864259c1f0765d52ebc53634d3ef8ef84a