don't generate a new Region when translating by 0,0

since regions are copy-on-write, this prevents to
duplicate the region entirely and offseting by 0,0 is
fairly common.

Change-Id: I9b8c286315a2e00dda01c2456397d72b5e12006b

libs/ui/Region.cpp

@@ -529,7 +529,7 @@ void Region::boolean_operation(int op, Region& dst,
 
 void Region::translate(Region& reg, int dx, int dy)
 {
-    if (!reg.isEmpty()) {
+    if ((dx || dy) && !reg.isEmpty()) {
 #if VALIDATE_REGIONS
         validate(reg, "translate (before)");
 #endif