introduce web_components pkg for consolidated polyfills

pkg/shadow_dom/lib/src/platform/patches-shadowdom-polyfill.js

-/*
- * Copyright 2013 The Polymer Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style
- * license that can be found in the LICENSE file.
- */
-(function() {
-  var ShadowDOMPolyfill = window.ShadowDOMPolyfill;
-  var wrap = ShadowDOMPolyfill.wrap;
-
-  // patch in prefixed name
-  Object.defineProperties(HTMLElement.prototype, {
-    //TODO(sjmiles): review accessor alias with Arv
-    webkitShadowRoot: {
-      get: function() {
-        return this.shadowRoot;
-      }
-    }
-  });
-
-  // ShadowCSS needs this:
-  window.wrap = window.ShadowDOMPolyfill.wrap;
-  window.unwrap = window.ShadowDOMPolyfill.unwrap;
-
-  //TODO(sjmiles): review method alias with Arv
-  HTMLElement.prototype.webkitCreateShadowRoot =
-      HTMLElement.prototype.createShadowRoot;
-
-  // TODO(jmesserly): we need to wrap document somehow (a dart:html hook?)
-  window.dartExperimentalFixupGetTag = function(originalGetTag) {
-    var NodeList = ShadowDOMPolyfill.wrappers.NodeList;
-    var ShadowRoot = ShadowDOMPolyfill.wrappers.ShadowRoot;
-    var unwrapIfNeeded = ShadowDOMPolyfill.unwrapIfNeeded;
-    function getTag(obj) {
-      // TODO(jmesserly): do we still need these?
-      if (obj instanceof NodeList) return 'NodeList';
-      if (obj instanceof ShadowRoot) return 'ShadowRoot';
-      if (window.MutationRecord && (obj instanceof MutationRecord))
-          return 'MutationRecord';
-      if (window.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 (obj !== unwrapped) {
-        // Fix up class names for Firefox.
-        // For some of them (like HTMLFormElement and HTMLInputElement),
-        // the "constructor" property of the unwrapped nodes points at the
-        // same constructor as the wrapper.
-        var ctor = obj.constructor
-        if (ctor === unwrapped.constructor) {
-          var name = ctor._ShadowDOMPolyfill$cacheTag_;
-          if (!name) {
-            name = Object.prototype.toString.call(unwrapped);
-            name = name.substring(8, name.length - 1);
-            ctor._ShadowDOMPolyfill$cacheTag_ = name;
-          }
-          return name;
-        }
-
-        obj = unwrapped;
-      }
-      return originalGetTag(obj);
-    }
-
-    return getTag;
-  };
-})();