rMOZILLARELEASE30cbe52bf370

Bug 1617974. Simplify OOMReporter setup. r=peterv

We don't really need the OOMReporterInstantiator bit. We can just use
FastErrorResult on the binding side, with casting to OOMReporter to ensure
callees take that, not an ErrorResult.

Differential Revision: https://phabricator.services.mozilla.com/D64184