Adds TCMalloc support for Android.

third_party/tcmalloc/chromium/src/maybe_threads.cc

Index: third_party/tcmalloc/chromium/src/maybe_threads.cc
diff --git a/third_party/tcmalloc/chromium/src/maybe_threads.cc b/third_party/tcmalloc/chromium/src/maybe_threads.cc
index 15c8a23dcb3509549ef6b45531f2418e988a3cf5..37646d6a50f40042ae70f591f14487246989f024 100644
--- a/third_party/tcmalloc/chromium/src/maybe_threads.cc
+++ b/third_party/tcmalloc/chromium/src/maybe_threads.cc
@@ -124,7 +124,17 @@ int perftools_pthread_once(pthread_once_t *ctl,
   if (pthread_once) {
     return pthread_once(ctl, init_routine);
   } else {
+#if defined(__ANDROID__)
+    // Android's pthread_once_t is typedef volatile and memcmp only takes
+    // const void*, cast the volatile away.
+    if (memcmp(const_cast<const void*>(reinterpret_cast<const volatile void*>(
+                   ctl)),
+               const_cast<const void*>(reinterpret_cast<const volatile void*>(
+                   &pthread_once_init)),
+               sizeof(*ctl)) == 0) {
+#else
     if (memcmp(ctl, &pthread_once_init, sizeof(*ctl)) == 0) {
+#endif
       init_routine();
       ++*(char*)(ctl);        // make it so it's no longer equal to init
     }