Make system layout fill the window properly on expanded desktop mode

This commit fixes e.g. the gap on the bottom of the lock screen
or the gap on the right side of status bar on landscape mode.

Patch set 2  : Remove whitespace issues
Patch set 3  : Code cleanup
Patch set 4  : Damn whitespace errors

Change-Id: Ic8a6b748f94d7dcc883201579d199898713c90fd