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

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

 [
   {
     "namespace": "callbacks",
     "types": [],
     "functions": [
       {
         "name": "returnsNothing",
         "type": "function",
         "description": "Takes nothing. Returns nothing.",
         "parameters": [
@@ skipping 51 matching lines @@
                 }
               }
             ]
           }
         ]
       }
     ]
   }
 ]