Enable use_allocator instead of linux_use_tcmalloc in Blink.

See the bug and http://crrev.com/255129 for the details.

BUG=345554
R=haraken@chromium.org, jamesr@chromium.org

Review URL: https://codereview.chromium.org/177053003

git-svn-id: svn://svn.chromium.org/blink/trunk@168591 bbb929c8-8fbe-4397-9dbb-9b2b20218538