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

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

 [
   {
     "namespace": "arrays",
     "types": [
       {
         "id": "EnumArrayType",
         "type": "object",
         "properties": {
           "types": {
             "type": "array",
@@ skipping 211 matching lines @@
                 "type": "array",
                 "items": {"$ref": "Item"}
               }
             ]
           }
         ]
       }
     ]
   }
 ]