This will only affect developers who are embedding Gecko, or
developers writing patches loading the prompt service via
getService.
In bug
1808115, we are replacing the embedded prompt service
contract ID (@mozilla.org/embedcomp/prompt-service;1)
with the main prompt service contract ID (@mozilla.org/prompter;1).
The embedded prompt service has been a simple wrapper around the
prompt service but with its own contract ID. It was kept around as
it was commonly used in the legacy add-on ecosystem. Therefore, we
are removing the now unnecessary duplicate.
Mark