Fix incorrect memory barrier usage I previously asked to be introduced.

base/message_loop/message_loop.cc

Index: base/message_loop/message_loop.cc
diff --git a/base/message_loop/message_loop.cc b/base/message_loop/message_loop.cc
index 93b9d0a2ec44bcc64567d197996faad652a242ff..f22eb9845a1a37bf51b3b163567474d35c314f9d 100644
--- a/base/message_loop/message_loop.cc
+++ b/base/message_loop/message_loop.cc
@@ -418,21 +418,13 @@ void MessageLoop::BindToCurrentThread() {
   unbound_task_runner_->BindToCurrentThread();
   unbound_task_runner_ = nullptr;
   SetThreadTaskRunnerHandle();
-  {
-    // Save the current thread's ID for potential use by other threads
-    // later from GetThreadName().
-    thread_id_ = PlatformThread::CurrentId();
-    subtle::MemoryBarrier();
-  }
+  thread_id_ = PlatformThread::CurrentId();
 }
 
 std::string MessageLoop::GetThreadName() const {
-  if (thread_id_ == kInvalidThreadId) {
-    // |thread_id_| may already have been initialized but this thread might not
-    // have received the update yet.
-    subtle::MemoryBarrier();
-    DCHECK_NE(kInvalidThreadId, thread_id_);
-  }
+  DCHECK_NE(kInvalidThreadId, thread_id_)
+      << "GetThreadName() must only be called after BindToCurrentThread()'s "
+      << "side-effects have been synchronized with this thread.";
   return ThreadIdNameManager::GetInstance()->GetName(thread_id_);
 }