Summary:
This change adds a `BlockIndexer` type which maintains pointers to
records that belong to the same process+thread pairs. The indexing
happens with order of appearance of records as they are visited.
This version of the indexer currently only supports FDR version 3 logs,
which contain `BufferExtent` records. We will add support for v2 and v1
logs in follow-up patches.
This is another part of D50441.
Reviewers: eizan, kpw, mboerger
Reviewed By: mboerger
Subscribers: mboerger, mgorny, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D51673
llvm-svn: 341518