The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9bcacc5a585b849f2076b1a11434e57e8b542779

commit 9bcacc5a585b849f2076b1a11434e57e8b542779
Author: Scott Violet <sky@chromium.org>
Date: Mon Mar 05 20:18:34 2018

Makes RemoteEventDispatcher callback run after client completes processing

This is necessary for tests that need to know an event has been
processed before they can continue on.

Writing tests for this uncovered a couple of bugs:
1. WindowManagerState::OnWillDestroyTree wasn't called correct, resulting in not
   cleaning up state correctly. This adds the call.
2. ProcessedEventTarget didn't deal with the tree being destroyed (only the
   window).

BUG= 817118 
TEST=covered by tests

Change-Id: If29d87e4ebc2bea9f9323a0489008f58aa6c4e32
Reviewed-on: https://chromium-review.googlesource.com/941517
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540910}
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/public/interfaces/remote_event_dispatcher.mojom
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/display.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/display.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/event_dispatcher.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/event_dispatcher.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/event_dispatcher_delegate.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/event_dispatcher_unittest.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/event_targeter_delegate.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/remote_event_dispatcher.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/test_change_tracker.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/test_utils.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/test_utils.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/window_manager_state.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/window_manager_state.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/window_manager_state_unittest.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/window_server.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/window_tree.cc
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/window_tree.h
[modify] https://crrev.com/9bcacc5a585b849f2076b1a11434e57e8b542779/services/ui/ws/window_tree_unittest.cc