[PATCH] D43341: [clang-doc] Implement reducer portion of the frontend framework

[Julie Hockett via Phabricator via cfe-commits]

juliehockett added a comment.

This will break things in clang-tools-extra without https://reviews.llvm.org/D46615, so I'm going to hold off landing this until that goes through


https://reviews.llvm.org/D43341