Exposing Point & Rect types

tools/dom/src/Rectangle.dart

Index: tools/dom/src/Rectangle.dart
diff --git a/tools/dom/src/Rectangle.dart b/tools/dom/src/Rectangle.dart
index 857a1992ebe2fc215a6c21df44dc59fcca154365..e87da1146b7cc1434b0a1a6569057750537ded52 100644
--- a/tools/dom/src/Rectangle.dart
+++ b/tools/dom/src/Rectangle.dart
@@ -13,14 +13,7 @@ class Rect {
   final num width;
   final num height;
 
-  Rect(this.left, this.top, this.width, this.height) {
-    if (width < 0) {
-      throw new ArgumentError(width);
-    }
-    if (height < 0) {
-      throw new ArgumentError(height);
-    }
-  }
+  const Rect(this.left, this.top, this.width, this.height);
 
   factory Rect.fromPoints(Point a, Point b) {
     var left;