Soon, DDS is going to support caching CPU profiles for a given user tag and provide an API for Flutter DevTools to request a cached profile. @bkonyi is working on this. We will use this functionality to support profiling app startup for Flutter apps. In order to use this functionality, we need a UserTag AppStartUp to be set at the beginning of app start, and unset at the end. This will mark the start and end times for app startup in the CPU profiler.

I'm not sure where in the flutter ecosystem these UserTag changes will need to take place. If either of them need to happen in Native code in the engine, @bkonyi can make a small change to the C API to support this. @chinmaygarde @iskakaushik

Flutter Tools will then need to pass AppStartUp, or whatever the name of the user tag ends up being, as a flag value to DDS, so that DDS knows to cache profiles for that tag. @jonahwilliams