Adding Element.AddHTML and Element.addText methods.

lib/html/dartium/html_dartium.dart

Index: lib/html/dartium/html_dartium.dart
diff --git a/lib/html/dartium/html_dartium.dart b/lib/html/dartium/html_dartium.dart
index 6edcdfa5c3453ddaf7a0587c3c6302f581728fd0..3d357199fa0e552bd11bb7f4eab6f110fbc16bc3 100644
--- a/lib/html/dartium/html_dartium.dart
+++ b/lib/html/dartium/html_dartium.dart
@@ -5918,6 +5918,14 @@ class _DocumentFragmentImpl extends _NodeImpl implements DocumentFragment {
     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>());
@@ -7104,14 +7112,14 @@ class _ElementRectImpl implements ElementRect {
 
   // TODO(jacobr): should we move these outside of ElementRect to avoid the
   // overhead of computing them every time even though they are rarely used.
-  final _ClientRectImpl _boundingClientRect; 
+  final _ClientRectImpl _boundingClientRect;
   final _ClientRectListImpl _clientRects;
 
   _ElementRectImpl(_ElementImpl element) :
     client = new _SimpleClientRect(element.$dom_clientLeft,
                                   element.$dom_clientTop,
-                                  element.$dom_clientWidth, 
-                                  element.$dom_clientHeight), 
+                                  element.$dom_clientWidth,
+                                  element.$dom_clientHeight),
     offset = new _SimpleClientRect(element.$dom_offsetLeft,
                                   element.$dom_offsetTop,
                                   element.$dom_offsetWidth,
@@ -7200,6 +7208,14 @@ class _ElementImpl extends _NodeImpl implements Element {
         new Completer<CSSStyleDeclaration>());
   }
 
+  void addText(String text) {
+    this.insertAdjacentText('beforeend', text);
+  }
+
+  void addHTML(String text) {
+    this.insertAdjacentHTML('beforeend', text);
+  }
+
   // Hooks to support custom WebComponents.
   var xtag;
 
@@ -26656,6 +26672,9 @@ interface Element extends Node, NodeSelector default _ElementFactoryProvider {
   AttributeMap get dataAttributes();
   void set dataAttributes(Map<String, String> value);
 
+  void addText(String text);
+  void addHTML(String html);
+
   /**
    * @domName getClientRects, getBoundingClientRect, clientHeight, clientWidth,
    * clientTop, clientLeft, offsetHeight, offsetWidth, offsetTop, offsetLeft,