Fix handling of cross-origin windows in dartium and better align general handling of different fram…

sdk/lib/html/html_common/conversions_dartium.dart

 part of html_common;
 
 convertDartToNative_PrepareForStructuredClone(value) =>
     new _StructuredCloneDartium().convertDartToNative_PrepareForStructuredClone(value);
 
 convertNativeToDart_AcceptStructuredClone(object, {mustCopy: false}) =>
     new _AcceptStructuredCloneDartium().convertNativeToDart_AcceptStructuredClone(object, mustCopy: mustCopy);
 
 class _StructuredCloneDartium extends _StructuredClone {
   newJsMap() => js.JsNative.newObject();
@@ skipping 249 matching lines @@
     while (prototype != null) {
       // We're a Dart class that's pointing to a JS class.
       var constructor = js.JsNative.getProperty(prototype, 'constructor');
       if (constructor != null) {          
         jsTypeName = js.JsNative.getProperty(constructor, 'name');
         type = getHtmlCreateType(jsTypeName);
         if (type != null) return type;
       }
       prototype = js.JsNative.getProperty(prototype, '__proto__');
     }
-  } catch (e, stacktrace) {
-    if (e is DebugAssertException) print("${e.message}\n ${stacktrace}");
-    else print("${stacktrace}");
+  } catch (e) {
+    // This case can happen for cross frame objects.
+    if (js.JsNative.hasProperty(e, "postMessage")) {

[Alan Knight, 2016/04/12 17:05:58]

Is this safe? There are quite a few other things with postMessage

[Jacob, 2016/04/12 17:08:51]

This is the exact same conversion used in dart2js. I agree it is not remotely
safe.

+      // assume this is a Window. To match Dart2JS, separate conversion code
+      // in dart:html will switch the wrapper to a cross frame window as
+      // required.
+      // TODO(jacobr): we could consider removing this code completely.
+      return Window.instanceRuntimeType;
+    }
   }
   return js.JSObject.instanceRuntimeType;
 }