Fixing analyzer warnings on overloading == but not get hashCode.

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 ///
 /// For examples, see
 /// [Dart HTML5 Samples](https://github.com/dart-lang/dart-html5-samples)
 /// on Github.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
@@ skipping 24490 matching lines @@
   String toString() {
     return '($left, $top, $width, $height)';
   }
 
   bool operator ==(other) {
     if (other is !Rect) return false;
     return left == other.left && top == other.top && width == other.width &&
         height == other.height;
   }
 
+  int get hashCode => JenkinsSmiHash.hash4(left.hashCode, top.hashCode,
+      width.hashCode, height.hashCode);
+
   /**
    * Computes the intersection of this rectangle and the rectangle parameter.
    * Returns null if there is no intersection.
    */
   Rect intersection(Rect rect) {
     var x0 = max(left, rect.left);
     var x1 = min(left + width, rect.left + rect.width);
 
     if (x0 <= x1) {
       var y0 = max(top, rect.top);
@@ skipping 3083 matching lines @@
 
   const Point([num x = 0, num y = 0]): x = x, y = y;
 
   String toString() => '($x, $y)';
 
   bool operator ==(other) {
     if (other is !Point) return false;
     return x == other.x && y == other.y;
   }
 
+  int get hashCode => JenkinsSmiHash.hash2(x.hashCode, y.hashCode);
+
   Point operator +(Point other) {
     return new Point(x + other.x, y + other.y);
   }
 
   Point operator -(Point other) {
     return new Point(x - other.x, y - other.y);
   }
 
   Point operator *(num factor) {
     return new Point(x * factor, y * factor);
@@ skipping 102 matching lines @@
   String toString() {
     return '($left, $top, $width, $height)';
   }
 
   bool operator ==(other) {
     if (other is !Rect) return false;
     return left == other.left && top == other.top && width == other.width &&
         height == other.height;
   }
 
+  int get hashCode => JenkinsSmiHash.hash4(left.hashCode, top.hashCode,
+      width.hashCode, height.hashCode);
+
   /**
    * Computes the intersection of this rectangle and the rectangle parameter.
    * Returns null if there is no intersection.
    */
   Rect intersection(Rect rect) {
     var x0 = max(left, rect.left);
     var x1 = min(left + width, rect.left + rect.width);
 
     if (x0 <= x1) {
       var y0 = max(top, rect.top);
@@ skipping 1190 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }