Name-based approach to cross frame support.

tests/lib_strong/html/cross_frame_test.dart

 import 'dart:html';
 
 import 'package:expect/minitest.dart';
 
 main() {
   var isWindowBase = predicate((x) => x is WindowBase, 'is a WindowBase');
   var isWindow = predicate((x) => x is Window, 'is a Window');
   var isLocationBase = predicate((x) => x is LocationBase, 'is a LocationBase');
   var isLocation = predicate((x) => x is Location, 'is a Location');
   var isHistoryBase = predicate((x) => x is HistoryBase, 'is a HistoryBase');
   var isHistory = predicate((x) => x is History, 'is a History');
 
   final iframe = new IFrameElement();
   document.body.append(iframe);
 
   test('window', () {
     expect(window, isWindow);
     expect(window.document, document);
   });
 
   test('iframe', () {
     final frameWindow = iframe.contentWindow;
     expect(frameWindow, isWindowBase);
     //TODO(gram) The next test should be written as:
     //    expect(frameWindow, isNot(isWindow));
     // but that will cause problems now until is/is! work
     // properly in dart2js instead of always returning true.
     expect(frameWindow is! Window, isTrue);
     expect(frameWindow.parent, isWindow);
-
-    // Ensure that the frame's document is inaccessible via window.
-    expect(() => frameWindow.document, throws);

[vsm, 2017/07/14 15:35:27]

Note - these are all static errors now.

-  });
-
-  test('contentDocument', () {
-    // Ensure that the frame's document is inaccessible.
-    expect(() => iframe.contentDocument, throws);
   });
 
   test('location', () {
     expect(window.location, isLocation);
     final frameLocation = iframe.contentWindow.location;
     expect(frameLocation, isLocationBase);
     // TODO(gram) Similar to the above, the next test should be:
     //     expect(frameLocation, isNot(isLocation));
     expect(frameLocation is! Location, isTrue);
 
-    expect(() => frameLocation.href, throws);
-    expect(() => frameLocation.hash, throws);
-
     final frameParentLocation = iframe.contentWindow.parent.location;
     expect(frameParentLocation, isLocation);
   });
 
   test('history', () {
     expect(window.history, isHistory);
     final frameHistory = iframe.contentWindow.history;
     expect(frameHistory, isHistoryBase);
     // See earlier comments.
     //expect(frameHistory, isNot(isHistory));
     expect(frameHistory is! History, isTrue);
 
     // Valid methods.
     frameHistory.forward();
 
-    expect(() => frameHistory.length, throws);
-
     final frameParentHistory = iframe.contentWindow.parent.history;
     expect(frameParentHistory, isHistory);
   });
 }