Add acquire/release to global variable.

base/debug/activity_tracker.h

Index: base/debug/activity_tracker.h
diff --git a/base/debug/activity_tracker.h b/base/debug/activity_tracker.h
index 53290e1b7070b7258a041fb672c3b912ea2eb32e..9ffcfaa844ba22ee9edee16dcade2481f5a4f011 100644
--- a/base/debug/activity_tracker.h
+++ b/base/debug/activity_tracker.h
@@ -748,7 +748,7 @@ class BASE_EXPORT GlobalActivityTracker {
   // Gets the global activity-tracker or null if none exists.
   static GlobalActivityTracker* Get() {
     return reinterpret_cast<GlobalActivityTracker*>(
-        subtle::NoBarrier_Load(&g_tracker_));
+        subtle::Acquire_Load(&g_tracker_));
   }
 
   // Gets the persistent-memory-allocator in which data is stored. Callers