DO NOT MERGE: InputDispatcher: Consider ownerPid in FLAG_OBSCURED calculations

Now that we are receiving an InputWindowHandle for each buffered surface
we need to take care not to introduce any behavior changes:
  1. Previously a SurfaceView on top of a main app window
     would not obscure that application for Input purposes (since
     it was unknown to InputDispatcher). We preserve this semantic
     by not considering windows from the same ownerPid as occluding
     eachother.
  2. However previously, windows WITH input channels from the same process
     would generate FLAG_OCCLUDED so we also preserve this semantic by
     only implementing the new semantic from 1 when channel is null.

Bug: 152064592
Test: ObscuredInputTests
Change-Id: If45acfd8b63c5ebd68bc219bc0fb6ee1c34650cd