This patch removes the C++ code used to run the minidump analyzer when a
content process crashes, and replaces it with JS code within the CrashService
object. This removes the need for a separate shutdown blocker in C++ code and
allows end-to-end testing of the crash service functionality. Additionally
the exception handler code can be simplified since it's now only used to run
the crash reporter client.
The test added to test_crash_service.js covers computing the minidump SHA256
hash (bug 1322611) and of the minidump analyzer itself (bug 1280477).
MozReview-Commit-ID: LO5w839NHev
