tcmalloc: pull in tcmalloc 2.7

This CL pulls in tcmalloc 2.7, the most recent release from upstream.
Places the files under vendor/ and makes a copy of the code under chromium/.

This CL did:
  # clone tcmalloc repository
  git clone https://github.com/gperftools/gperftools vendor

  # checkout the new version and remove git metadata
  cd vendor && git checkout gperftools-2.7 && rm -rf .git

  # mirror the src folder
  cd .. && rsync -av --delete vendor/src/ chromium/src/

This is code pulled from upstream.
NOPRESUBMIT=true

BUG=724399,b:70905156

Change-Id: I3a3510d514de15a8b1463725fa6f7dab9b1e6d0e
Reviewed-on: https://chromium-review.googlesource.com/1130671
Reviewed-by: Will Harris <wfh@chromium.org>
Commit-Queue: Gabriel Marin <gmx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576221}
509 files changed