ASurfaceControl: fix surface damage

There are two problems with surface control.
1) By merging the rects, the Region turned into 0,0,0,0 instead of
an or of the Rects.
2) In the case where an app intends to have a region of 0,0,0,0,
we should treat it the same as a region of 0,0,-1,-1.

Bug: 131175047
Test: ASurfaceControl
Change-Id: Ib2e3b90ac215e069d3d3c2eca81ff1013b4287aa