Adds TCMalloc support for Android.

third_party/tcmalloc/chromium/src/maybe_threads.cc

 // Copyright (c) 2005, Google Inc.
 // All rights reserved.
 // 
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 // 
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 102 matching lines @@
   // is not linked with -pthread).
   static bool pthread_once_ran_before_threads = false;
   if (pthread_once_ran_before_threads) {
     return 0;
   }
   if (!__isthreaded) {
     init_routine();
     pthread_once_ran_before_threads = true;
     return 0;
   }
-#endif
+#elif defined(__ANDROID__)
+  // Android >= 2.3 (GB) always implement pthread_once.
+  return pthread_once(ctl, init_routine);
+#else
   if (pthread_once) {
     return pthread_once(ctl, init_routine);
   } else {
     if (memcmp(ctl, &pthread_once_init, sizeof(*ctl)) == 0) {
       init_routine();
       ++*(char*)(ctl);        // make it so it's no longer equal to init
     }
     return 0;
   }
+#endif
 }