Added test scenarios around nested clusters

Nested cluster behavior is now defined as "pretend nested
clusters are not clusters". This adds some testing for that.

Bug: 32804858
Test: ViewGroupTest#{testAddKeyboardNavigationClusters,
      testRestoreFocusInCluster, testTouchscreenBlocksFocus}
Change-Id: I2f7082659f7eec9f2f0e7e6d9c04a8230bcc6295
1 file changed