mash: remove the LockStateControllerDelegate.

This removes the LockStateControllerDelegate and mojoifys/renames it
into the ShutdownClient, which is exported by chrome.

While in the long term, we'll want to move the code that's currently in
ShutdownClient into ash (and either use CrosSettings in ash or send
messages to a dedicated CrosSettings service), the chromeos device
settings code is sufficiently intertangled with the browser process that
it isn't happening anytime soon. (See crbug.com/446937)

BUG=628792
TEST=covered by converted ash_unittests; manually tested the mojo call in non-mash ash.

Review-Url: https://codereview.chromium.org/2471643002
Cr-Commit-Position: refs/heads/master@{#429471}

• ash/BUILD.gn[diff]
• ash/accelerators/accelerator_controller_unittest.cc[diff]
• ash/public/interfaces/BUILD.gn[diff]
• ash/public/interfaces/shutdown.mojom[Added - diff]
• ash/shell.cc[diff]
• ash/test/BUILD.gn[diff]
• ash/test/lock_state_controller_test_api.cc[Added - diff]
• ash/test/lock_state_controller_test_api.h[Added - diff]
• ash/test/test_lock_state_controller_delegate.cc[Deleted - diff]
• ash/test/test_lock_state_controller_delegate.h[Deleted - diff]
• ash/test/test_shutdown_client.cc[Added - diff]
• ash/test/test_shutdown_client.h[Added - diff]
• ash/wm/lock_state_controller.cc[diff]
• ash/wm/lock_state_controller.h[diff]
• ash/wm/lock_state_controller_unittest.cc[diff]
• ash/wm/shutdown_client_proxy.cc[Added - diff]
• ash/wm/shutdown_client_proxy.h[Added - diff]
• chrome/app/mash/chrome_mash_content_browser_manifest_overlay.json[diff]
• chrome/browser/chrome_content_browser_manifest_overlay.json[diff]
• chrome/browser/chromeos/BUILD.gn[diff]
• chrome/browser/chromeos/chrome_interface_factory.cc[diff]
• chrome/browser/chromeos/power/login_lock_state_notifier.cc[diff]
• chrome/browser/chromeos/power/session_state_controller_delegate_chromeos.h[Deleted - diff]
• chrome/browser/chromeos/power/shutdown_client_impl.cc[Renamed from chrome/browser/chromeos/power/session_state_controller_delegate_chromeos.cc - diff]
• chrome/browser/chromeos/power/shutdown_client_impl.h[Added - diff]