In DevTools, we need a way to connect Flutter.Frame events (sent here) to their corresponding timeline events on the UI and Raster threads. This is a requirement in order to make the DevTools timeline show live frame data.

We cannot connect a Flutter.Frame event to its corresponding timeline events by timestamp because the two data sources use different clocks. From @iskakaushik:

Based on some initial observations, there doesn't seem to be an easy way to convert between Dart Timeline and Flutter Clocks. For example, on iOS, Dart timeline seems to use "mach_absolute_time" which doesn't increment when the system is asleep, whereas in Flutter we use "std::chrono::steady_clock()" which is independent of the system uptime.

If we could add metadata to the root UI thread and root Raster thread event that would allow us to associate those two timeline events with a Flutter.Frame event, that would work. Perhaps adding an arg "frameNumber" that matches the "number" field from Flutter.Frame events.