Unsuppress/fix most indexeddb tests on Dartium

sdk/lib/html/html_common/conversions_dartium.dart

Index: sdk/lib/html/html_common/conversions_dartium.dart
diff --git a/sdk/lib/html/html_common/conversions_dartium.dart b/sdk/lib/html/html_common/conversions_dartium.dart
index c66ce174da09ed1f06450c2c8b6a601c7055b408..d6e606464dfd496221be385328adc28b35ebaad1 100644
--- a/sdk/lib/html/html_common/conversions_dartium.dart
+++ b/sdk/lib/html/html_common/conversions_dartium.dart
@@ -62,3 +62,7 @@ Future convertNativePromiseToDartFuture(js.JsObject promise) {
     .callMethod("catch", [(result) => completer.completeError(result)]);
   return completer.future;
 }
+
+convertDartToNative_DateTime(DateTime date) {
+  return new js.JsObject(js.context["Date"], [date.millisecondsSinceEpoch]);
+}