GitLab

These will be necessary to get the StatusAreaWidget to display in mojo:ash.

* Fork ash::sysui::ShellDelegateMus into //ash/mus
* Convert WmShell constructors to take ShellDelegate via unique_ptr
* Use ash::KeyboardUI for now, rather than KeyboardUIMus
* Move GPUSupport and PointerWatcherDelegate to //ash/common
* Fix some IWYU

No functional changes for regular non-mash chrome.

BUG=619636
TEST=ash_unittests, run chrome --mash manually and no crashes

Review-Url: https://codereview.chromium.org/2150023002
Cr-Commit-Position: refs/heads/master@{#405594}