Roll forward to cl/333580336

Signed-off-by: Josh Nohle <nohle@google.com>

cpp/platform_v2/impl/ios/atomic_boolean.h

@@ -0,0 +1,28 @@
+#ifndef PLATFORM_V2_IMPL_IOS_ATOMIC_BOOLEAN_H_
+#define PLATFORM_V2_IMPL_IOS_ATOMIC_BOOLEAN_H_
+
+#include <atomic>
+
+#include "platform_v2/api/atomic_boolean.h"
+
+namespace location {
+namespace nearby {
+namespace ios {
+
+class AtomicBoolean : public api::AtomicBoolean {
+ public:
+  explicit AtomicBoolean(bool initial_value) : value_(initial_value) {}
+  ~AtomicBoolean() override = default;
+
+  bool Get() const override { return value_.load(); }
+  bool Set(bool value) override { return value_.exchange(value); }
+
+ private:
+  std::atomic_bool value_;
+};
+
+}  // namespace ios
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_V2_IMPL_IOS_ATOMIC_BOOLEAN_H_