[ozone/platform] Add support for menu window type

In particular, there is now a PlatformWindowInitProperties structure,
which brings initial properties to ozone windows. It can be initialized
(in the future, when other code is in place) with a desired window type,
bounds and parenting model, which is very important for Wayland's
xdg_popup windows (used for menu windows, for example).

Bug: 578890
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;luci.chromium.try:linux_vr
Change-Id: I573912d462d698b19b1bb09cf687971965e951e0
Reviewed-on: https://chromium-review.googlesource.com/1068746
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567601}
17 files changed