Use limited JavaStringBuilder implementation instead of Dart StringBuffer.

pkg/analyzer-experimental/lib/src/generated/html_scanner.dart

 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.html.scanner;
 
 import 'dart:collection';
 import 'java_core.dart';
 import 'source.dart';
 import 'error.dart';
 import 'instrumentation.dart';
@@ skipping 1092 matching lines @@
   String get content {
     Token token = _attributeEnd.next;
     if (identical(token, _contentEnd)) {
       return "";
     }
     String content = token.lexeme;
     token = token.next;
     if (identical(token, _contentEnd)) {
       return content;
     }
-    StringBuffer buffer = new StringBuffer();
+    JavaStringBuilder buffer = new JavaStringBuilder();
     while (token != _contentEnd) {
-      buffer.write(token.lexeme);
+      buffer.append(token.lexeme);
       token = token.next;
     }
     return buffer.toString();
   }
   /**
    * Answer the token (not {@code null}) after the content, which may be
    * <ul>
    * <li>(1) {@link TokenType#LT_SLASH} for nodes with open and close tags, or</li>
    * <li>(2) the {@link TokenType#LT} nodeStart of the next sibling node if this node is self
    * closing or the attributeEnd is {@link TokenType#SLASH_GT}, or</li>
@@ skipping 126 matching lines @@
    * to edit the AST structure.
    * @return the children (not {@code null}, contains no {@code null}s)
    */
   List<XmlTagNode> get tagNodes => _tagNodes;
   void visitChildren(XmlVisitor<Object> visitor) {
     for (XmlTagNode node in _tagNodes) {
       node.accept(visitor);
     }
   }
 }