Update idlsync.py to pull in dependencies required for chrome api generation.

third_party/chrome/tools/json_schema_compiler/test/choices.json

 [
   {
     "namespace": "choices",
     "types": [
       {
         "id": "ChoiceType",
         "type": "object",
         "properties": {
           "integers": {
             "choices": [
@@ skipping 130 matching lines @@
                  ],
                 "description": "Some integers."
               }
             ]
           }
         ]
       }
     ]
   }
 ]