Change Rectangle.operator== to compare right/bottom instead of width/height.

tests/lib/math/rectangle_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library rect_test;
 
 import 'dart:math';
 import 'package:unittest/unittest.dart';
 
 main() {
@@ skipping 110 matching lines @@
   });
 
   test('hashCode', () {
     var a = new Rectangle(0, 1, 2, 3);
     var b = new Rectangle(0, 1, 2, 3);
     expect(a.hashCode, b.hashCode);
 
     var c = new Rectangle(1, 0, 2, 3);
     expect(a.hashCode == c.hashCode, isFalse);
   });
+
+  {  // Edge cases for boundingBox/intersection
+    edgeTest(a, l) {
+      test('edge case $a/$l', () {
+        var r = new Rectangle(a, a, l, l);
+        expect(r.boundingBox(r), r);
+        expect(r.intersection(r), r);
+      });
+    }
+
+    var bignum1 = 0x20000000000000 + 0.0;
+    var bignum2 = 0x20000000000002 + 0.0;
+    var bignum3 = 0x20000000000004 + 0.0;
+    edgeTest(1.0, bignum1);
+    edgeTest(1.0, bignum2);
+    edgeTest(1.0, bignum3);
+    edgeTest(bignum1, 1.0);
+    edgeTest(bignum2, 1.0);
+    edgeTest(bignum3, 1.0);
+  }
+
+  test("equality with different widths", () {
+    var bignum = 0x80000000000008 + 0.0;
+    var r1 = new Rectangle(bignum, bignum, 1.0, 1.0);
+    var r2 = new Rectangle(bignum, bignum, 2.0, 2.0);
+    expect(r1, r2);
+    expect(r1.hashCode, r2.hashCode);
+    expect(r1.right, r2.right);
+    expect(r1.bottom, r2.bottom);
+    expect(r1.width, 1.0);
+    expect(r2.width, 2.0);
+  });
 }