Lockscreen quick affordance buttons are bigger now.

There was a bug where the lock screen buttons were too small. This CL
fixes that bug.

The reason they were to slow is because we added the selection border to
them, which required the addition of an inset that made the visible
area of the background that much smaller, even when the selection border
is not visible.

The approach taken in the CL is simple. Use the foreground for the
selection border. Note that it does remove the spacing between the
visible background and the border, but that's fine as the selection
border is only ever shown in a scaled-down preview of the lock screen.

Fix: 265974363
Test: manually verified the size and functionality on the lock screen
Test: manually verified the selection border is visible in wallpaper
picker

Change-Id: I3d1c82df8830a1c1125b01e95b73310dd8f67b07