DevTools performance page broken when using systrace recorder

When launching an app with `--trace-systrace`, the performance tab in DevTools just spins, and JS console shows the following:

@bkonyi is there a way for us to check at runtime which timeline recorder is being used? If the systrace recorder is in use, in DevTools we should gate our logic that depends on timeline events from the VM service and we should provide the user with instructions on how to load this trace into DevTools from file or into ui.perfetto.dev directly.