dwds: Breakpoints in part files do not display in Dart Devtools

Setting breakpoints inside a part file in Dart Devtools the visual indication doesn't show up. This can be seen by modifying a trivial stagehand simple-web app to add a part file and adding a breakpoint. The breakpoints do get set, and fire, so it's just a display issues. It might be a devtools bug, or it might be that dwds is not following the protocol correctly.

Reproduce the issue with a trivial stagehand simple-web app that uses a part file, then set a breakpoint in Dart Devtools and compare the displayed state with a breakpoint in the main file. Trace how dwds reports breakpoint locations through the debugging protocol. Done means breakpoints in part files receive the expected visual indication while still firing.

Written by the indexing model from the issue text.