Revert "Implementing polyfills for insertAdjacent* to get them working on FF."

lib/dom/templates/html/impl/impl_DocumentFragment.darttemplate

Index: lib/dom/templates/html/impl/impl_DocumentFragment.darttemplate
diff --git a/lib/dom/templates/html/impl/impl_DocumentFragment.darttemplate b/lib/dom/templates/html/impl/impl_DocumentFragment.darttemplate
index 264184ae883a19f115386e7a97691a86de3c0c4a..643e1b10d1e99580ee639f31eb455fed5cafa243 100644
--- a/lib/dom/templates/html/impl/impl_DocumentFragment.darttemplate
+++ b/lib/dom/templates/html/impl/impl_DocumentFragment.darttemplate
@@ -197,14 +197,6 @@ class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
     this._insertAdjacentNode(where, new DocumentFragment.html(text));
   }
 
-  void addText(String text) {
-    this.insertAdjacentText('beforeend', text);
-  }
-
-  void addHTML(String text) {
-    this.insertAdjacentHTML('beforeend', text);
-  }
-
   Future<ElementRect> get rect() {
     return _createMeasurementFuture(() => const EmptyElementRect(),
                                     new Completer<ElementRect>());