This change will add a handler for the WIN+L key combination on non-home SKUs
of Windows.  When the WIN+L combo is pressed, we will call LockWorkstation.

Based on my investigation, it appears that this combo cannot be overridden and
only works when issued from a physical keyboard.  Therefore it isn't something
that can be issued remotely and our function call will not conflict with some
other behavior.  We skip the Home SKUs as locking the workstation doesn't
really make sense there (it brings up the switch users UI instead).

BUG=517322

Review-Url: https://codereview.chromium.org/1930473003
Cr-Commit-Position: refs/heads/master@{#390673}