Add acquire/release to global variable.

base/debug/activity_tracker.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Activity tracking provides a low-overhead method of collecting information
 // about the state of the application for analysis both while it is running
 // and after it has terminated unexpectedly. Its primary purpose is to help
 // locate reasons the browser becomes unresponsive by providing insight into
 // what all the various threads and processes are (or were) doing.
 
@@ skipping 730 matching lines @@
   // Like above but internally creates an allocator using local heap memory of
   // the specified size. This is used primarily for unit tests.
   static void CreateWithLocalMemory(size_t size,
                                     uint64_t id,
                                     StringPiece name,
                                     int stack_depth);
 
   // 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
   // can store additional records here to pass more information to the
   // analysis process.
   PersistentMemoryAllocator* allocator() { return allocator_.get(); }
 
   // Gets the thread's activity-tracker if it exists. This is inline for
   // performance reasons and it uses thread-local-storage (TLS) so that there
   // is no significant lookup time required to find the one for the calling
@@ skipping 306 matching lines @@
   ScopedProcessWaitActivity(const void* program_counter,
                             const base::Process* process);
   DISALLOW_COPY_AND_ASSIGN(ScopedProcessWaitActivity);
 };
 #endif
 
 }  // namespace debug
 }  // namespace base
 
 #endif  // BASE_DEBUG_ACTIVITY_TRACKER_H_