Don't relayout based on a window that isn't visible

The method commitFinishDrawingLocked returned true even if the window
it was called for was hidden. By returning the value that
performShowLocked() returns it only returns true if the window is
shown.

Fixes bug 19100757.

Change-Id: I45df70aedcb3909561fd3a19e861579a11521db9
1 file changed