[PATCH] [sanitizer] Add a fast version of StackDepotGet() for use in LSan. Add a class that holds a snapshot of the StackDepot optimized for querying by ID. This allows us to speed up LSan dramatically.

[Sergey Matveev]

  As a side note, I think we should stop prefixing everything with "Internal".

  It really only makes sense when we're reimplementing a standard library function under the same name.

http://llvm-reviews.chandlerc.com/D1496

BRANCH
  fix/stackdepot

ARCANIST PROJECT
  compiler-rt