Don't apply AA to rects with no rotation/perspective.

Change-Id: I21138d4d0589cc28f1dcffb8b675cd81a9900e24
diff --git a/libs/hwui/Matrix.h b/libs/hwui/Matrix.h
index 08f5d77..2fa6ab7 100644
--- a/libs/hwui/Matrix.h
+++ b/libs/hwui/Matrix.h
@@ -111,6 +111,7 @@
     }
 
     bool isPureTranslate();
+    bool isSimple();
 
     bool changesBounds();