[CP] Fix ConcurrentModificationError in DDS #130739
Description
Issue Link
Commit Hash
https://dart-review.googlesource.com/c/sdk/+/313782
Target
beta
PR Link
Changelog Description
Before iterating over debug client breakpoints, copy the URIs to a new list because the handling within the loop is asynchronous, so other code paths could mutate the hash map storing them (leading to a ConcurrentModificationError).
Impacted Users
Any Flutter developers doing debugging
Impact Description
If a user adds/removes a breakpoint while the debugger code is sending the list of breakpoints to an isolate, their flutter tool may crash with a ConcurrentModificationError, and they will lose their entire debugger session (they will have to add their breakpoints from scratch once the tool restarts.
Workaround
Only add/remove breakpoints before the app has started.
Risk
low
Test Coverage
yes
Validation Steps
No response