| This empty folder exists to harmonize "built-in" metrics | 
 | work with the "metric extension" functionality of trace processor. | 
 |  | 
 | Essentially by adding a protos folder, we can pass | 
 | src/trace_processor/metrics as an extension path to shell to | 
 | override all built-in metrics. This means we can change the SQL | 
 | files *without* needing to recompile trace processor. | 
 |  | 
 | In the future, we might also move the protos here but that would | 
 | be a bigger change which would need coordination across repos ( | 
 | e.g. Chrome because of the metrics autoroller for Chrome metrics). |