title: Difference between specifying a view as isRoot() & withId
body: <p>I want to know the difference in specifying a view in different ways</p>
  <p>onView(withId(R.id.btnAuthLogin)).perform(click());</p>
  <p>onView(isRoot()).perform(waitId(R.id.btnAuthLogin, 1000));</p>
  <p><strong>It's not the delay thing that i want to know</strong></p>
  <p>What happens when we specify isRoot() rather than specifying withID.</p>
  <p>Hope there is no confusion.</p>