Add union types to the analysis server API spec.

pkg/analysis_server/tool/spec/codegen_matchers.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 generation for the file "matchers.dart".
  */
 library codegen.matchers;
 
 import 'dart:convert';
@@ skipping 169 matching lines @@
       }
       writeln();
     });
     write('}');
   }
 
   @override
   void visitTypeReference(TypeReference typeReference) {
     write(camelJoin(['is', typeReference.typeName]));
   }
+
+  @override
+  void visitTypeUnion(TypeUnion typeUnion) {
+    bool commaNeeded = false;
+    write('isOneOf([');
+    for (TypeDecl choice in typeUnion.choices) {
+      if (commaNeeded) {
+        write(', ');
+      }
+      visitTypeDecl(choice);
+      commaNeeded = true;
+    }
+    write('])');
+  }
 }
 
 /**
  * Translate spec_input.html into protocol_matchers.dart.
  */
 main() {
   CodegenMatchersVisitor visitor = new CodegenMatchersVisitor(readApi());
   String code = visitor.collectCode(visitor.visitApi);
   File outputFile = new File('../../test/integration/protocol_matchers.dart');
   outputFile.writeAsStringSync(code);
 }