Is your feature request related to a problem? Please describe.
I've noted that we need to wait for the initial analysis to happen for custom requests like Open Diagnostics Page to respond. Also, if the server is doing some heavy computation (reanalysing many libraries without fine-grained, for example), it also gets stuck.

Describe the solution you'd like
I'd like Dart-Code to display a progress indication about these requests so that I don't request them more than once, thinking they didn't get through.