Fix some issues when building Closure runner.jar

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': [
     {
@@ skipping 20 matching lines @@
       'outputs': [
         '<(out_file)',
       ],
       'action': [
         'python',
         '<(CLOSURE_DIR)/checker.py',
         '<(source_file)',
         '--depends', '<@(depends)',
         '--externs', '<@(externs)',
         '--out_file', '<(out_file)',
-        # Add '--verbose', for glorious log spam.
+        # Add '--verbose' for make glorious log spam of Closure compiler.
       ],
       'message': 'Compiling <(source_file)',
     }
   ],
 }