The next patch converts the memory reporting architecture to use the "returns"
feature of IPDL, and mozilla::ipc::RejectCallback does not have a return
type, so this patch removes the return value.
FinishReportingCallback::Callback() needs to remain an XPCOM method
that returns NS_OK because it is called from JS during testing.
Differential Revision: https://phabricator.services.mozilla.com/D85498
The guts of MemoryReportRequestClient's supporting runnables contain
switches on the particular type of process we're running. If you're
bringing up a new process type, having to add extra cases for your
process type here is a bit onerous. These runnables really shouldn't
know anything about the process types that they're running on, either.
The easiest thing to do is modify MemoryReportRequestClient::Start to
take callbacks for what to do when a report is created and when
reporting is finished. Then all process-specific knowledge can be
pushed out to the clients themselves, leaving MemoryReportRequestClient
and friends process-type agnostic. We could even, at some later date,
move this code into xpcom/base/ to sit near nsMemoryReporterManager,
where it belongs.