dwds cannot find a frame in a caller after asynchronous gap

**Repro**

- Debug flutter hello_world example
- Set breakpoint in binding.dart on line 993 as shown in the image
- Start debugging
- When app is stopped on the breakpoint, click on `scheduleAttachRootWidget` function down the the stack past the asynchronous gap
- Type `rootWidget` in the expression evaluation box

**Result**

InternalError: No frame with index 9

**Expected**

expression evaluated successfully


Reproduce this in the Flutter hello_world example using the breakpoint in binding.dart at line 993, then select scheduleAttachRootWidget past the asynchronous gap and evaluate rootWidget. Trace the frame lookup used by expression evaluation; done means the expression evaluates successfully instead of returning “No frame with index 9”.

Written by the indexing model from the issue text.