Avoid documenting canonicalization 'example' library from polymer

utils/apidoc/docgen.gyp

 # Copyright (c) 2012, 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.
 
 {
   'variables' : {
     'script_suffix%': '',
   },
   'conditions' : [
     ['OS=="win"', {
@@ skipping 62 matching lines @@
             'python',
             '../../tools/only_in_release_mode.py',
             '<@(_outputs)',
             '--',
             '../../sdk/bin/dart',
             '--package-root=<(PRODUCT_DIR)/packages',
             '../../pkg/docgen/bin/docgen.dart',
             '--out=<(PRODUCT_DIR)/api_docs/docgen',
             '--json',
             '--include-sdk',
+            '--no-include-dependent-packages',
             '--package-root=<(PRODUCT_DIR)/packages',
             '--exclude-lib=async_helper',
             '--exclude-lib=expect',
             '--exclude-lib=docgen',
+            '--exclude-lib=canonicalization.a',
+            '--exclude-lib=canonicalization.b',
+            '--exclude-lib=canonicalization.c',
+            '--exclude-lib=canonicalization.d',
             '../../pkg',          
           ],
           'message': 'Running docgen: <(_action)',
         },
       ],
     }
   ],
 }