Roll Observatory packages and add a roll script

web_components/lib/interop.dart

-// Copyright (c) 2014, 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.
-
-/// Provides support for associating a Dart type for Javascript Custom Elements.
-/// This will not work unless `dart_support.js` is loaded.
-library web_components.interop;
-
-import 'dart:html' show document, Element;
-import 'dart:js' show JsObject, JsFunction;
-
-final _doc = new JsObject.fromBrowserObject(document);
-
-/// Returns whether [registerDartType] is supported, which requires to have
-/// `dart_support.js` already loaded in the page.
-bool get isSupported => _doc.hasProperty('_registerDartTypeUpgrader');
-
-/// Watches when Javascript custom elements named [tagName] are created and
-/// associates the created element with the given [dartType]. Only one Dart type
-/// can be registered for a given tag name.
-void registerDartType(String tagName, Type dartType, {String extendsTag}) {
-  if (!isSupported) {
-    throw new UnsupportedError("Couldn't find "
-        "`document._registerDartTypeUpgrader`. Please make sure that "
-        "`packages/web_components/interop_support.html` is loaded and "
-        "available before calling this function.");
-  }
-
-  var upgrader =
-      document.createElementUpgrader(dartType, extendsTag: extendsTag);
-
-  // Unfortunately the dart:html upgrader will throw on an already-upgraded
-  // element, so we need to duplicate the type check to prevent that.
-  // An element can be upgraded twice if it extends another element and calls
-  // createdCallback on the superclass. Since that's a valid use case we must
-  // wrap at both levels, and guard against it here.
-  upgradeElement(e) {
-    if (e.runtimeType != dartType) upgrader.upgrade(e);
-  }
-
-  _doc.callMethod('_registerDartTypeUpgrader', [tagName, upgradeElement]);
-}
-
-/// 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');