Launch kiosk apps from Login screen "Apps" menu.

Bug: 836861
Change-Id: Ib480dfa25b45a1cc6dd1424e8f84d0891eec1a0e
Reviewed-on: https://chromium-review.googlesource.com/1092095
Commit-Queue: Quan Nguyen <qnnguyen@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568560}

• ash/login/login_screen_controller.cc[diff]
• ash/login/login_screen_controller.h[diff]
• ash/login/mock_login_screen_client.h[diff]
• ash/login/ui/login_keyboard_test_base.cc[diff]
• ash/public/interfaces/login_screen.mojom[diff]
• ash/shelf/login_shelf_view.cc[diff]
• ash/shelf/login_shelf_view_unittest.cc[diff]
• chrome/browser/chromeos/BUILD.gn[diff]
• chrome/browser/chromeos/login/app_launch_controller.cc[diff]
• chrome/browser/chromeos/login/app_launch_controller.h[diff]
• chrome/browser/chromeos/login/ui/kiosk_app_menu_updater.cc[Added - diff]
• chrome/browser/chromeos/login/ui/kiosk_app_menu_updater.h[Added - diff]
• chrome/browser/chromeos/login/ui/login_display_host_mojo.cc[diff]
• chrome/browser/chromeos/login/ui/login_display_host_mojo.h[diff]
• chrome/browser/chromeos/login/ui/oobe_ui_dialog_delegate.cc[diff]
• chrome/browser/chromeos/login/ui/oobe_ui_dialog_delegate.h[diff]
• chrome/browser/ui/ash/login_screen_client.cc[diff]
• chrome/browser/ui/ash/login_screen_client.h[diff]