Get rid of ===/!===.

lib/html/src/dart2js_DOMImplementation.dart

Index: lib/html/src/dart2js_DOMImplementation.dart
diff --git a/lib/html/src/dart2js_DOMImplementation.dart b/lib/html/src/dart2js_DOMImplementation.dart
index 955841c2aa488b0be06926565a387e7103f22425..4ea123d34fb504fee1072625086180e4ad007a59 100644
--- a/lib/html/src/dart2js_DOMImplementation.dart
+++ b/lib/html/src/dart2js_DOMImplementation.dart
@@ -46,7 +46,7 @@ class _DOMWindowCrossFrameImpl implements Window {
   _DOMWindowCrossFrameImpl(this._window);
 
   static Window _createSafe(w) {
-    if (w === window) {
+    if (identical(w, window)) {
       return w;
     } else {
       // TODO(vsm): Cache or implement equality.
@@ -70,7 +70,7 @@ class _LocationCrossFrameImpl implements Location {
   _LocationCrossFrameImpl(this._location);
 
   static Location _createSafe(location) {
-    if (location === window.location) {
+    if (identical(location, window.location)) {
       return location;
     } else {
       // TODO(vsm): Cache or implement equality.
@@ -95,7 +95,7 @@ class _HistoryCrossFrameImpl implements History {
   _HistoryCrossFrameImpl(this._history);
 
   static History _createSafe(h) {
-    if (h === window.history) {
+    if (identical(h, window.history)) {
       return h;
     } else {
       // TODO(vsm): Cache or implement equality.