The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/100dccedb99065973e21ecf0661d123e719784e1

commit 100dccedb99065973e21ecf0661d123e719784e1
Author: kylechar <kylechar@chromium.org>
Date: Fri Oct 28 22:19:16 2016

Handle primary display changes in mustash.

This CL adds code to propagate the primary display id from
PlatformScreen to the WS, then from the WS to all mus clients.

1. Rename display.mojom to display_manager.mojom to reflect the main
   interface name.
2. Add primary and internal display id to the OnDisplays() message.
3. Add OnPrimaryDisplayChanged() message for when the primary display
   changes.
4. Improve platform_screen_ozone_unittests. Track the ordering of events
   to ensure the expected events happen in the expected order.
5. Fix some ordering problems with PlatformScreenOzone.

BUG= 657125 

Review-Url: https://codereview.chromium.org/2461513002
Cr-Commit-Position: refs/heads/master@{#428517}

[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/display/platform_screen_delegate.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/display/platform_screen_ozone.cc
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/display/platform_screen_ozone.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/display/platform_screen_ozone_unittests.cc
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/public/interfaces/BUILD.gn
[delete] https://crrev.com/beee5025a4557f5ea443e7583aa508a26d85ad3d/services/ui/public/interfaces/display.mojom
[add] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/public/interfaces/display_manager.mojom
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/public/interfaces/window_manager_constants.mojom
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/service.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/display.cc
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/display.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/display_manager.cc
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/display_manager.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/test_utils.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/user_display_manager.cc
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/user_display_manager.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/user_display_manager_delegate.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/user_display_manager_unittest.cc
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/services/ui/ws/window_manager_state.h
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/ui/views/mus/screen_mus.cc
[modify] https://crrev.com/100dccedb99065973e21ecf0661d123e719784e1/ui/views/mus/screen_mus.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9825bba32903429ea01835f6cd6761b67dbd5a26

commit 9825bba32903429ea01835f6cd6761b67dbd5a26
Author: kylechar <kylechar@chromium.org>
Date: Wed Nov 02 14:10:16 2016

Fix namespace and primary display in ScreenBase.

ScreenBase has unnecessary display:: namespaces all over. Remove them.
Also update GetPrimaryDisplay() to not crash if there is no primary
display.

BUG= 657125 

Review-Url: https://codereview.chromium.org/2472553002
Cr-Commit-Position: refs/heads/master@{#429270}

[modify] https://crrev.com/9825bba32903429ea01835f6cd6761b67dbd5a26/ui/display/screen_base.cc
[modify] https://crrev.com/9825bba32903429ea01835f6cd6761b67dbd5a26/ui/display/screen_base.h

Kyle, is this still an issue with simplified display management?

Nope, this is all done since ash now initiates changes to the primary display id.