merge to trunk all changes from 36817 until 37378 under the packages: polymer,

pkg/web_components/lib/interop.dart

Index: pkg/web_components/lib/interop.dart
===================================================================
--- pkg/web_components/lib/interop.dart	(revision 37373)
+++ pkg/web_components/lib/interop.dart	(working copy)
@@ -31,3 +31,13 @@
       dartType, extendsTag: extendsTag);
   _doc.callMethod('_registerDartTypeUpgrader', [tagName, upgrader.upgrade]);
 }
+
+/// This function is mainly used to save resources. By default, we save a log of
+/// elements that are created but have no Dart type associated with them. This
+/// is so we can upgrade them as soon as [registerDartType] is invoked. This
+/// function can be called to indicate that we no longer are interested in
+/// logging element creations and that it is sufficient to only upgrade new
+/// elements as they are being created. Typically this is called after the last
+/// call to [registerDartType] or as soon as you know that no element will be
+/// created until the call to [registerDartType] is made.
+void onlyUpgradeNewElements() => _doc.callMethod('_onlyUpgradeNewElements');