Adjust timer layout for multiwindow

Bug: 26840878

Timer circles and stopwatch circles, when displayed, are always 60%
of the container width in portrait or 90% of the container height in
landscape.

When the parent container falls below 320dp width and height, the
circles may disappear as they are too small to remain useful.

Change-Id: Ice7fb1ccd4db9abd215141e427e1f8ddd4b64fc0