strengthen region validation

Change-Id: I75ee7bc4dd7a2f5357ac8994a23bc8b8bfb6eb44
diff --git a/include/ui/Region.h b/include/ui/Region.h
index 0049fde..43a4450 100644
--- a/include/ui/Region.h
+++ b/include/ui/Region.h
@@ -161,7 +161,8 @@
     static void translate(Region& reg, int dx, int dy);
     static void translate(Region& dst, const Region& reg, int dx, int dy);
 
-    static bool validate(const Region& reg, const char* name);
+    static bool validate(const Region& reg,
+            const char* name, bool silent = false);
     
     // mStorage is a (manually) sorted array of Rects describing the region
     // with an extra Rect as the last element which is set to the