Rolling forward https://codereview.chromium.org/1155683008/ which was

third_party/closure_compiler/compile.py

 #!/usr/bin/python
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Runs Closure compiler on JavaScript files to check for errors and produce
 minified output."""
 
 import argparse
 import os
@@ skipping 400 matching lines @@
   parser.add_argument("--success-stamp",
                       help="Timestamp file to update upon success")
 
   parser.set_defaults(single_file=True, strict=False)
   opts = parser.parse_args()
 
   depends = opts.depends or []
   externs = set(opts.externs or [])
 
   polymer_externs = os.path.join(os.path.dirname(_CURRENT_DIR), 'polymer',
-                                 'v0_8', 'components-chromium',
+                                 'v1_0', 'components-chromium',
                                  'polymer-externs', 'polymer.externs.js')
   externs.add(polymer_externs)
 
   checker = Checker(verbose=opts.verbose, strict=opts.strict)
   if opts.single_file:
     for source in opts.sources:
       depends, externs = build.inputs.resolve_recursive_dependencies(
           source, depends, externs)
       found_errors, _ = checker.check(source, out_file=opts.out_file,
                                       depends=depends, externs=externs,
                                       output_wrapper=opts.output_wrapper)
       if found_errors:
         sys.exit(1)
   else:
     found_errors, stderr = checker.check_multiple(
         opts.sources,
         out_file=opts.out_file,
         output_wrapper=opts.output_wrapper,
         externs=externs)
     if found_errors:
       print stderr
       sys.exit(1)
 
   if opts.success_stamp:
     with open(opts.success_stamp, "w"):
       os.utime(opts.success_stamp, None)