Add a flag to the compiler for compiling polymer code.

third_party/closure_compiler/compile_js.gypi

 # 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.
 {
   'type': 'none',
   'variables': {
     'CLOSURE_DIR': '<(DEPTH)/third_party/closure_compiler',
   },
   'actions': [
     {
       # This action optionally takes these arguments:
       # - depends: scripts that the source file depends on being included already
       # - externs: files that describe globals used by |source|
       'action_name': 'compile_js',
       'variables': {
         'source_file': '<(_target_name).js',
         'out_file': '<(SHARED_INTERMEDIATE_DIR)/closure/<!(python <(CLOSURE_DIR)/build/outputs.py <@(source_file))',
         'externs%': [],
         'depends%': [],
+        'polymer%': 0,
       },
       'inputs': [
         'compile_js.gypi',
         '<(CLOSURE_DIR)/compile.py',
         '<(CLOSURE_DIR)/processor.py',
         '<(CLOSURE_DIR)/build/inputs.py',
         '<(CLOSURE_DIR)/build/outputs.py',
         '<(CLOSURE_DIR)/compiler/compiler.jar',
         '<(CLOSURE_DIR)/runner/runner.jar',
         '<!@(python <(CLOSURE_DIR)/build/inputs.py <(source_file) -d <@(depends) -e <@(externs))',
       ],
       'outputs': [
         '<(out_file)',
       ],
       'action': [
         'python',
         '<(CLOSURE_DIR)/compile.py',
         '<(source_file)',
         '--depends', '<@(depends)',
         '--externs', '<@(externs)',
         '--out_file', '<(out_file)',
+        '--polymer', '<(polymer)',
         # Add '--verbose' for make glorious log spam of Closure compiler.
       ],
       'message': 'Compiling <(source_file)',
     }
   ],
 }