I believe the right thing here is for second-level embeddings the owner supplies the LocalSurfaceId. For top-level embeddings, ws2 should provide the LocalSurfaceId.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/42d66957878b2372abc62f54b2d33f9308a956f3

commit 42d66957878b2372abc62f54b2d33f9308a956f3
Author: Scott Violet <sky@chromium.org>
Date: Mon Jun 04 16:12:17 2018

reland: ash: makes WindowService deal with LocalSurfaceId correctly

For first-level embeddings WindowService should assign LocalSurfaceIds. For all
others the LocalSurfaceId should come from the client.

BUG= 844789 
TEST=covered by tests
TBR=xiyuan@chromium.org

Change-Id: I1f0a06729f0099414985e1e0712ae9b713b28dbe
Reviewed-on: https://chromium-review.googlesource.com/1085373
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564110}
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/BUILD.gn
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/ime/ime_focus_handler_unittest.cc
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/public/cpp/immersive/immersive_fullscreen_controller.cc
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/public/cpp/immersive/immersive_fullscreen_controller.h
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/public/cpp/immersive/immersive_fullscreen_controller_test_api.cc
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/public/cpp/immersive/immersive_fullscreen_controller_test_api.h
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/shelf/shelf_layout_manager_unittest.cc
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/test/ash_test_base.cc
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/test/ash_test_base.h
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/test/ash_test_helper.cc
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/test/ash_test_helper.h
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/wm/workspace/workspace_layout_manager_unittest.cc
[modify] https://crrev.com/42d66957878b2372abc62f54b2d33f9308a956f3/ash/ws/window_service_owner.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bf6eb7d79da7a4841273397d1e6e38a8ae025698

commit bf6eb7d79da7a4841273397d1e6e38a8ae025698
Author: Scott Violet <sky@chromium.org>
Date: Mon Jun 04 20:00:40 2018

ash: makes WindowService deal with LocalSurfaceId correctly

For first-level embeddings WindowService should assign LocalSurfaceIds. For all
others the LocalSurfaceId should come from the client.

BUG= 844789 
TEST=covered by tests

Change-Id: I91d7db419d2267ade3b9e185c5dc09e318a30a13
Reviewed-on: https://chromium-review.googlesource.com/1083134
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564201}
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/client_root.cc
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/client_root.h
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/client_window.h
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/window_service_client.cc
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/window_service_client.h
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/window_service_client_test_helper.cc
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/window_service_client_test_helper.h
[modify] https://crrev.com/bf6eb7d79da7a4841273397d1e6e38a8ae025698/services/ui/ws2/window_service_client_unittest.cc