Adding PIP input consumer.

- This CL provides the framework for manipulating the pinned stack using
  an input policy (to be determined later) provided by the SystemUI.

Test: android.server.cts.ActivityManagerPinnedStackTests
Test: #testNonTappablePipActivity

Change-Id: I025c41fff26ed05a35d68e59f10330680ed11ea8
1 file changed