Update include/base headers for C++11/14 (see issue #3140)

See the issue for update guidelines.

libcef_dll/base/cef_atomic_flag.cc

@@ -0,0 +1,31 @@
+// Copyright (c) 2011 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.
+
+#include "include/base/cef_atomic_flag.h"
+
+#include "include/base/cef_logging.h"
+
+namespace base {
+
+AtomicFlag::AtomicFlag() {
+  // It doesn't matter where the AtomicFlag is built so long as it's always
+  // Set() from the same sequence after. Note: the sequencing requirements are
+  // necessary for IsSet()'s callers to know which sequence's memory operations
+  // they are synchronized with.
+  set_thread_checker_.DetachFromThread();
+}
+
+AtomicFlag::~AtomicFlag() = default;
+
+void AtomicFlag::Set() {
+  DCHECK(set_thread_checker_.CalledOnValidThread());
+  flag_.store(1, std::memory_order_release);
+}
+
+void AtomicFlag::UnsafeResetForTesting() {
+  set_thread_checker_.DetachFromThread();
+  flag_.store(0, std::memory_order_release);
+}
+
+}  // namespace base