Add union types to the analysis server API spec.

pkg/analysis_server/tool/spec/codegen_inttest_methods.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 "integration_test_methods.dart".
  */
 library codegenInttestMethods;
 
 import 'dart:convert';
@@ skipping 215 matching lines @@
         case 'String':
         case 'int':
         case 'bool':
           // These types correspond exactly to Dart types
           return type.typeName;
         case 'object':
           return 'Map<String, dynamic>';
         default:
           throw new Exception(type.typeName);
       }
+    } else if (type is TypeUnion) {
+      return 'Object';
     } else {
       throw new Exception('Unexpected kind of TypeDecl');
     }
   }
 }
 
 /**
  * Translate spec_input.html into protocol_matchers.dart.
  */
 main() {
   CodegenInttestMethodsVisitor visitor = new CodegenInttestMethodsVisitor(
       readApi());
   String code = visitor.collectCode(visitor.visitApi);
   File outputFile = new File(
       '../../test/integration/integration_test_methods.dart');
   outputFile.writeAsStringSync(code);
 }