Add copyright header to generated analyzer files.

pkg/analyzer/test/generated/scanner_test.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.
+
 // 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.scanner_test;
 
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/java_junit.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/scanner.dart';
@@ skipping 2304 matching lines @@
   }
 }
 
 main() {
   CharSequenceReaderTest.dartSuite();
   IncrementalScannerTest.dartSuite();
   KeywordStateTest.dartSuite();
   ScannerTest.dartSuite();
   TokenTypeTest.dartSuite();
 }