exo: Reparent pointer surface

When the display configuration changes, the pointer surface must be
reparented to the new primary display. A client-side bug previously
forced a surface change on pointer enter, causing the surface to be
reparented to the latest primary display.

BUG=730843
TEST=Verify correct parenting by printing window hierarchy.

Review-Url: https://codereview.chromium.org/2934953002
Cr-Commit-Position: refs/heads/master@{#479073}
2 files changed