Make Dartium JS interop implementation more robust in the presence of JS paths that touch dart:html…

tests/html/js_typed_interop_test.dart

 // Copyright (c) 2015, 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.
 
 @JS()
 library js_typed_interop_test;
 
 import 'dart:html';
 
 import 'package:js/js.dart';
@@ skipping 68 matching lines @@
   function confuse(obj) { return obj; }
 
   function StringWrapper(str) {
     this.str = str;
   }
   StringWrapper.prototype = {
     charCodeAt: function(index) {
       return this.str.charCodeAt(index);
     }
   };
+  function getCanvasContext() {
+    return document.createElement('canvas').getContext('2d');
+  }
+  window.windowProperty = 42;
+  document.documentProperty = 45;
 """);
 }
 
 class RegularClass {
   factory RegularClass(a) {
     return new RegularClass.fooConstructor(a);
   }
   RegularClass.fooConstructor(this.a);
   var a;
 }
@@ skipping 70 matching lines @@
 @JS()
 class StringWrapper {
   external StringWrapper(String str);
   external int charCodeAt(int i);
 }
 
 // Defeat JS type inference by calling through JavaScript interop.
 @JS()
 external confuse(obj);
 
+@JS()
+external CanvasRenderingContext2D getCanvasContext();
+
+@JS('window.window.document.documentProperty')
+external num get propertyOnDocument;
+
+@JS('window.self.window.window.windowProperty')
+external num get propertyOnWindow;
+
 main() {
   _injectJs();
 
   useHtmlIndividualConfiguration();
 
   group('object literal', () {
     test('simple', () {
       var l = new ExampleLiteral(x: 3, y: "foo");
       expect(l.x, equals(3));
       expect(l.y, equals("foo"));
@@ skipping 178 matching lines @@
 
       // We do know at runtime whether something is a JsArray or not.
       expect(foo is List, isFalse);
     });
 
     test('dart interfaces', () {
       expect(foo is Function, isFalse);
       expect(selection is List, isTrue);
     });
   });
+  group('html', () {
+    test('return html type', () {
+      expect(getCanvasContext() is CanvasRenderingContext2D, isTrue);
+    });
+    test('js path contains html types', () {

[Alan Knight, 2015/11/04 18:44:14]

nit: Not clear to me what this testing.

[Jacob, 2015/11/04 19:01:30]

This case would fail previously 
note the path to propertyOnWindow intentionally bounces back between types that
were auto-proxied with the old dart:js JsObject class.

+      expect(propertyOnWindow, equals(42));
+      expect(propertyOnDocument, equals(45));
+    });
+  });
 }