SPM: Update display id on primary display changes

When the primary display is changed to an existing display, it is
done by swapping the display ids the two relevant WindowTreeHosts.
There is no bounds change or window hierarchy change. Hence the
client of Window Service is not aware that the underlying display
id is changed. This causes WindowEventDispatcher to not finding
correct root for touch events. The CL fixes the issue by updating
WS client with the changed display ids.

Bug: 936984, b/125458515
Change-Id: Ib6b46903fced804ac8ad2a506cc9a12f0ad003e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1497475
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637420}
12 files changed