Version Used: 3.6.0-3.20209.3

Steps to Reproduce:

1. JS/TS VS extension imports IVsTypeScriptTodoCommentService in order to call ReportTodoComments. On DocumentAdded and DocumentChanged workspace events we call into ReportTodoComments.
   See PR: https://devdiv.visualstudio.com/DevDiv/_git/TypeScript-VS/pullrequest/240324

Expected Behavior:
Calls to ReportTodoComments work and the comments appear in the Task List

Actual Behavior:
The calls fail because Roslyn has not finished loading

Ideally, one of the following would be true:

1. The service to be available by the time any workspace change events are fired
2. Some way to check if the service is available so that we can buffer any requests and wait to send them only when the service is available