appendHtml, when sanitizing, should create document fragment in the right context

tools/dom/templates/html/impl/impl_Element.darttemplate

Index: tools/dom/templates/html/impl/impl_Element.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Element.darttemplate b/tools/dom/templates/html/impl/impl_Element.darttemplate
index b2b4188691dbb051b438e5a74241751b72eb9c6d..c8fd179a1b564f10c9232d48c14fb2cdaf022d7d 100644
--- a/tools/dom/templates/html/impl/impl_Element.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Element.darttemplate
@@ -1037,7 +1037,7 @@ $endif
       if (treeSanitizer is _TrustedHtmlTreeSanitizer) {
         _insertAdjacentHtml(where, html);
       } else {
-        _insertAdjacentNode(where, new DocumentFragment.html(html,
+        _insertAdjacentNode(where, createFragment(html,
             validator: validator, treeSanitizer: treeSanitizer));
       }
   }
@@ -1328,11 +1328,6 @@ $endif
     if (_parseDocument == null) {
       _parseDocument = document.implementation.createHtmlDocument('');
       _parseRange = _parseDocument.createRange();
-
-      // Workaround for Chrome bug 229142- URIs are not resolved in new doc.
-      var base = _parseDocument.createElement('base');
-      base.href = document.baseUri;
-      _parseDocument.head.append(base);
     }
     var contextElement;
     if (this is BodyElement) {
@@ -1342,7 +1337,8 @@ $endif
       _parseDocument.body.append(contextElement);
     }
     var fragment;
-    if (Range.supportsCreateContextualFragment) {
+    if (Range.supportsCreateContextualFragment &&
+        _canBeUsedToCreateContextualFragment) {
       _parseRange.selectNodeContents(contextElement);
       fragment = _parseRange.createContextualFragment(html);
     } else {
@@ -1364,6 +1360,24 @@ $endif
     return fragment;
   }
 
+  /** Test if createContextualFragment is supported for this element type */
+  bool get _canBeUsedToCreateContextualFragment =>
+      !_cannotBeUsedToCreateContextualFragment;
+
+  /** Test if createContextualFragment is NOT supported for this element type */
+  bool get _cannotBeUsedToCreateContextualFragment =>
+      _tagsForWhichCreateContextualFragmentIsNotSupported.contains(tagName);
+
+  /**
+   * A hard-coded list of the tag names for which createContextualFragment
+   * isn't supported.
+   */
+  static const _tagsForWhichCreateContextualFragmentIsNotSupported =
+      const ['HEAD', 'AREA',
+      'BASE', 'BASEFONT', 'BR', 'COL', 'COLGROUP', 'EMBED', 'FRAME', 'FRAMESET',
+      'HR', 'IMAGE', 'IMG', 'INPUT', 'ISINDEX', 'LINK', 'META', 'PARAM',
+      'SOURCE', 'STYLE', 'TITLE', 'WBR'];
+
   /**
    * Parses the HTML fragment and sets it as the contents of this element.
    *