Added compile-time define to add "initial-exec" attribute.

third_party/tcmalloc/chromium/src/thread_cache.h

Index: third_party/tcmalloc/chromium/src/thread_cache.h
diff --git a/third_party/tcmalloc/chromium/src/thread_cache.h b/third_party/tcmalloc/chromium/src/thread_cache.h
index 529402908450e9efb3f06708cdbd6dbecc7c7236..2e1dd2365a6b0875b83dcea5dbc9c23ee720eac1 100644
--- a/third_party/tcmalloc/chromium/src/thread_cache.h
+++ b/third_party/tcmalloc/chromium/src/thread_cache.h
@@ -259,7 +259,13 @@ class ThreadCache {
   // a good tradeoff for us.
 #ifdef HAVE_TLS
   static __thread ThreadCache* threadlocal_heap_
-# ifdef HAVE___ATTRIBUTE__
+  // http://code.google.com/p/chromium/issues/detail?id=124489
+  // This code is being linked into pyautolib.so file for Chrome. A bug has
+  // been filed here:
+  // http://code.google.com/p/chromium/issues/detail?id=124489
+  // Ideally pyautolib.so should not link against this code. The current
+  // workaround is to pass in -DPGO_GENERATE.

[gpike, 2012/04/24 18:38:21]

Please improve the comment. Under what circumstances is -DPGO_GENERATE supposed
to be used? Is Chrome still going to get the performance benefit of
initial-exec?

+#if defined(HAVE___ATTRIBUTE__) && ! defined(PGO_GENERATE)

[Alexander Potapenko, 2012/04/24 10:38:15]

I think "!defined" is more common in Chromium.

[asharif1, 2012/04/24 17:50:12]

Done.

    __attribute__ ((tls_model ("initial-exec")))
 # endif
    ;