[profile] Fix binary format reader error propagation.

Summary:
This was originally part of rL328132, and led to the discovery
of the issues addressed in rL328987. Re-landing.

Reviewers: xur, davidxl, bkramer

Reviewed By: bkramer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45545

llvm-svn: 330029