Introduce CryptAuthGCMManager, which handles GCM interactions for CryptAuth.

components/proximity_auth/cryptauth/cryptauth_gcm_manager.cc

+// Copyright 2015 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 "components/proximity_auth/cryptauth/cryptauth_gcm_manager.h"
+
+#include "base/prefs/pref_registry_simple.h"
+#include "components/proximity_auth/cryptauth/pref_names.h"
+
+namespace proximity_auth {
+
+CryptAuthGCMManager::Observer::~Observer() {
+}
+
+void CryptAuthGCMManager::Observer::OnGCMRegistrationResult(bool success) {
+}
+
+void CryptAuthGCMManager::Observer::OnReenrollMessage() {
+}
+
+void CryptAuthGCMManager::Observer::OnResyncMessage() {
+}
+
+// static.
+void CryptAuthGCMManager::RegisterPrefs(PrefRegistrySimple* registry) {
+  registry->RegisterStringPref(prefs::kCryptAuthGCMRegistrationId,
+                               std::string());
+}
+
+}  // namespace proximity_auth