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web_components/lib/dart_support.js

-// 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.
-
-// Teaches dart2js about the wrapping that is done by the Shadow DOM polyfill.
-(function() {
-  var ShadowDOMPolyfill = window.ShadowDOMPolyfill;
-  if (!ShadowDOMPolyfill) return;
-
-  // TODO(sigmund): remove the userAgent check once 1.6 rolls as stable.
-  // See: dartbug.com/18463
-  if (navigator.dartEnabled || (navigator.userAgent.indexOf('(Dart)') !== -1)) {
-    console.error("ShadowDOMPolyfill polyfill was loaded in Dartium. This " +
-        "will not work. This indicates that Dartium's Chrome version is " +
-        "not compatible with this version of web_components.");
-  }
-
-  var needsConstructorFix = window.constructor === window.Window;
-
-  // TODO(jmesserly): we need to wrap document somehow (a dart:html hook?)
-
-  // dartNativeDispatchHooksTransformer is described on initHooks() in
-  // sdk/lib/_internal/lib/native_helper.dart.
-  if (typeof window.dartNativeDispatchHooksTransformer == 'undefined')
-    window.dartNativeDispatchHooksTransformer = [];
-
-  window.dartNativeDispatchHooksTransformer.push(function(hooks) {
-    var NodeList = ShadowDOMPolyfill.wrappers.NodeList;
-    var ShadowRoot = ShadowDOMPolyfill.wrappers.ShadowRoot;
-    var unwrapIfNeeded = ShadowDOMPolyfill.unwrapIfNeeded;
-    var originalGetTag = hooks.getTag;
-    hooks.getTag = function getTag(obj) {
-      // TODO(jmesserly): do we still need these?
-      if (obj instanceof NodeList) return 'NodeList';
-      if (obj instanceof ShadowRoot) return 'ShadowRoot';
-      if (MutationRecord && (obj instanceof MutationRecord))
-          return 'MutationRecord';
-      if (MutationObserver && (obj instanceof MutationObserver))
-          return 'MutationObserver';
-
-      // TODO(jmesserly): this prevents incorrect interaction between ShadowDOM
-      // and dart:html's <template> polyfill. Essentially, ShadowDOM is
-      // polyfilling native template, but our Dart polyfill fails to detect this
-      // because the unwrapped node is an HTMLUnknownElement, leading it to
-      // think the node has no content.
-      if (obj instanceof HTMLTemplateElement) return 'HTMLTemplateElement';
-
-      var unwrapped = unwrapIfNeeded(obj);
-      if (unwrapped && (needsConstructorFix || obj !== unwrapped)) {
-        // Fix up class names for Firefox, or if using the minified polyfill.
-        // dart2js prefers .constructor.name, but there are all kinds of cases
-        // where this will give the wrong answer.
-        var ctor = obj.constructor
-        if (ctor === unwrapped.constructor) {
-          var name = ctor._ShadowDOMPolyfill$cacheTag_;
-          if (!name) {
-            name = originalGetTag(unwrapped);
-            ctor._ShadowDOMPolyfill$cacheTag_ = name;
-          }
-          return name;
-        }
-
-        obj = unwrapped;
-      }
-      return originalGetTag(obj);
-    }
-  });
-})();