Add union types to the analysis server API spec.

pkg/analysis_server/tool/spec/to_html.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Code for displaying the API as HTML.  This is used both for generating a
  * full description of the API as a web page, and for generating doc comments
  * in generated code.
  */
 library to.html;
@@ skipping 177 matching lines @@
   void visitTypeReference(TypeReference typeReference) {
     String displayName = typeReference.typeName;
     if (api.types.containsKey(typeReference.typeName)) {
       link('type_${typeReference.typeName}', () {
         write(displayName);
       });
     } else {
       write(displayName);
     }
   }
+
+  @override
+  void visitTypeUnion(TypeUnion typeUnion) {
+    bool verticalBarNeeded = false;
+    for (TypeDecl choice in typeUnion.choices) {
+      if (verticalBarNeeded) {
+        write(' | ');
+      }
+      visitTypeDecl(choice);
+      verticalBarNeeded = true;
+    }
+  }
 }
 
 /**
  * Visitor that records the mapping from HTML elements to various kinds of API
  * nodes.
  */
 class ApiMappings extends HierarchicalApiVisitor {
   ApiMappings(Api api) : super(api);
 
   Map<dom.Element, Domain> domains = <dom.Element, Domain>{};
@@ skipping 326 matching lines @@
  */
 main() {
   ToHtmlVisitor visitor = new ToHtmlVisitor(readApi());
   dom.Document document = new dom.Document();
   for (dom.Node node in visitor.collectHtml(visitor.visitApi)) {
     document.append(node);
   }
   File outputFile = new File('../../doc/api.html');
   outputFile.writeAsStringSync(document.outerHtml);
 }