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

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

 [
   {
     "namespace": "enums",
     "types": [
       {
         "id": "Enumeration",
         "type": "string",
         "enum": ["one", "two", "three"]
       },
       {
@@ skipping 192 matching lines @@
           {
             "name": "secondEnum",
             "type": "string",
             "enum": ["spam", "ham", "eggs"]
           }
         ]
       }
     ]
   }
 ]