tcmalloc: Honor HEAPPROFILE envvar only in profiling=1 builds.

tcmalloc: Honor HEAPPROFILE envvar only in profiling=1 builds.

Several systems in chromium (about:tracing, some code in blink) use
tcmalloc's heap profiler, so keep most of it around.  Do disable support
for the HEAPPROFILE envvar, and for the exit-time dump to "Exiting" (unless in
profiling=1 builds), as that causes a static initializer.

BUG=94925
R=willchan@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=271415

[willchan no longer on Chromium, 2014-05-19 17:17:09]

lgtm

[Nico, 2014-05-19 17:39:22]

Committed patchset #1 manually as r271415 (presubmit successful).