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

Review URL: https://codereview.chromium.org/295583002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271415 0039d316-1c4b-4281-b951-d872f2087c98

third_party/tcmalloc/README.chromium

@@ -97,3 +97,4 @@ Modifications:
 - Fix logging issues in android
 - Changed DEFINE_foo macros to ignore envname unless ENABLE_PROFILING is defined
 - Changed DEFINE_string to define const char*s instead of strings
+- Disabled HEAPPROFILE envvar unless ENABLE_PROFILING is defined

third_party/tcmalloc/chromium/src/heap-profiler.cc

@@ -662,7 +662,7 @@ extern "C" void HeapProfilerDumpAliveObjects(const char* filename) {
 //----------------------------------------------------------------------
 // Initialization/finalization code
 //----------------------------------------------------------------------
-
+#if defined(ENABLE_PROFILING)
 // Initialization code
 static void HeapProfilerInit() {
   // Everything after this point is for setting up the profiler based on envvar
@@ -693,3 +693,4 @@ struct HeapProfileEndWriter {
 static const TCMallocGuard tcmalloc_initializer;
 REGISTER_MODULE_INITIALIZER(heapprofiler, HeapProfilerInit());
 static HeapProfileEndWriter heap_profile_end_writer;
+#endif   // defined(ENABLE_PROFILING)