remove most string concat, fixes #7

lib/dom.dart

 /// A simple tree API that results from parsing html. Intended to be compatible
 /// with dart:html, but it is missing many types and APIs.
 library dom;
 
 // TODO(jmesserly): lots to do here. Originally I wanted to generate this using
 // our Blink IDL generator, but another idea is to directly use the excellent
 // http://dom.spec.whatwg.org/ and http://html.spec.whatwg.org/ and just
 // implement that.
 
 import 'dart:collection';
@@ skipping 384 matching lines @@
   }
 
   void _addOuterHtml(StringBuffer str) {
     str.write(toString());
   }
 
   DocumentType clone(bool deep) => new DocumentType(name, publicId, systemId);
 }
 
 class Text extends Node {
-  String data;
+  /// The text node's data, stored as either a String or StringBuffer.
+  /// We support storing a StringBuffer here to support fast [appendData].
+  /// It will flatten back to a String on read.
+  var _data;
 
-  Text(this.data) : super._();
+  Text(String data) : _data = data != null ? data : '', super._();
 
   int get nodeType => Node.TEXT_NODE;
 
+  String get data => _data = _data.toString();
+  set data(String value) {
+    _data = value != null ? value : '';
+  }
+
   String toString() => '"$data"';
 
   void _addOuterHtml(StringBuffer str) => writeTextNodeAsHtml(str, this);
 
   Text clone(bool deep) => new Text(data);
 
+  void appendData(String data) {
+    if (_data is! StringBuffer) _data = new StringBuffer(_data);
+    StringBuffer sb = _data;
+    sb.write(data);
+  }
+
   String get text => data;
   set text(String value) {
     data = value;
   }
 }
 
 // TODO(jmesserly): Elements should have a pointer back to their document
 class Element extends Node with _ParentNode, _ElementAndDocument {
   final String namespaceUri;
 
@@ skipping 105 matching lines @@
   set innerHtml(String value) {
     nodes.clear();
     // TODO(jmesserly): should be able to get the same effect by adding the
     // fragment directly.
     nodes.addAll(parseFragment(value, container: localName).nodes);
   }
 
   void _addOuterHtml(StringBuffer str) {
     // http://www.whatwg.org/specs/web-apps/current-work/multipage/the-end.html#serializing-html-fragments
     // Element is the most complicated one.
-    str.write('<${_getSerializationPrefix(namespaceUri)}$localName');
+    str.write('<');
+    str.write(_getSerializationPrefix(namespaceUri));
+    str.write(localName);
 
     if (attributes.length > 0) {
       attributes.forEach((key, v) {
         // Note: AttributeName.toString handles serialization of attribute
         // namespace, if needed.
-        str.write(' $key="${htmlSerializeEscape(v, attributeMode: true)}"');
+        str.write(' ');
+        str.write(key);
+        str.write('="');
+        str.write(htmlSerializeEscape(v, attributeMode: true));
+        str.write('"');
       });
     }
 
     str.write('>');
 
     if (nodes.length > 0) {
       if (localName == 'pre' ||
           localName == 'textarea' ||
           localName == 'listing') {
         final first = nodes[0];
@@ skipping 410 matching lines @@
 
 class _ConcatTextVisitor extends TreeVisitor {
   final _str = new StringBuffer();
 
   String toString() => _str.toString();
 
   visitText(Text node) {
     _str.write(node.data);
   }
 }