GitLab

ActivationChangeObserver -> WmActivationObserver.
Always create RootWindowControllerObserverImpl.
Make RootWindowControllerObserverImpl add/remove itself.

Compare display ids instead of root windows.
Use wm::GetWindowForFullscreenMode instead of ash::RWC.
Use WmLookup instead of WmWindowAura::Get.
Use Widget::IsMouseEventsEnabled instead of CursorClient.
Fix IWYU issues; remove unused forward decls/friends.

BUG=631215
TEST=Automated tests; no behavior changes.
R=jamescook@chromium.org

Review-Url: https://codereview.chromium.org/2187513003
Cr-Commit-Position: refs/heads/master@{#408271}