[Closure Externs] Handle optional params sent to an API callback

tools/json_schema_compiler/js_util.py

 # Copyright 2015 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.
 
 from code import Code
 from model import PropertyType
 
 from datetime import datetime
 
 LICENSE = """// Copyright %s The Chromium Authors. All rights reserved.
@@ skipping 101 matching lines @@
     else:
       c.Concat(self._TypeToJsType(namespace_name, js_type), new_line=False)
     c.Append('}', new_line=False)
 
   def _FunctionToJsFunction(self, namespace_name, function):
     """Converts a model.Function to a JS type (i.e., function([params])...)"""
     c = Code()
     c.Append('function(')
     for i, param in enumerate(function.params):
       c.Concat(self._TypeToJsType(namespace_name, param.type_), new_line=False)
+      if param.optional:
+        c.Append('|undefined', new_line=False)
       if i is not len(function.params) - 1:
         c.Append(', ', new_line=False, strip_right=False)
     c.Append('):', new_line=False)
 
     if function.returns:
       c.Concat(self._TypeToJsType(namespace_name, function.returns),
                new_line=False)
     else:
       c.Append('void', new_line=False)
 
@@ skipping 40 matching lines @@
     """Returns a @see link for a given API 'object' (type, method, or event).
     """
 
     # NOTE(devlin): This is kind of a hack. Some APIs will be hosted on
     # developer.chrome.com/apps/ instead of /extensions/, and some APIs have
     # '.'s in them (like app.window), which should resolve to 'app_window'.
     # Luckily, the doc server has excellent url resolution, and knows exactly
     # what we mean. This saves us from needing any complicated logic here.
     return ('@see https://developer.chrome.com/extensions/%s#%s-%s' %
                 (namespace_name, object_type, object_name))