tree 3ebcd88b671b12e4e36a1894ad0a96f4cd268bea
parent 0bc7c5294bc93815cb33242319ec59c7f62eb2b0
author chaviw <chaviw@google.com> 1591654052 -0700
committer chaviw <chaviw@google.com> 1591719036 -0700

Maintain Z order for all layers in offscreen hierarchy

There was already code in place to ensure that z order was maintained in
the offscreen tree. However, this didn't work if a layer was moved to become
a child of an offscreen layer. The z order was only maintained beneath
the new offscreen layer, not the entire subtree.

This change uses the root of the offscreen subtree to ensure the z order
is maintained even when new offscreen layers are added to the subtree.

Fixes: 157188227
Test: IME gets correct relative z
Test: RelativeZTest.LayerWithRelativeReparentedToOffscreen
Change-Id: I62553ce245dacd2a8684d8bb02de67f60ddc6774