Add ScopedKeepAlive to c/b/lifetime

chrome/browser/lifetime/keep_alive_registry.cc

+// 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.
+
+#include "chrome/browser/lifetime/keep_alive_registry.h"
+
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/lifetime/application_lifetime.h"
+#include "chrome/browser/lifetime/keep_alive_options.h"
+
+namespace {
+
+// Helper function to remove one item from the multisets.
+void RemoveOne(const KeepAliveOptions* key,
+               std::multiset<const KeepAliveOptions*>& container) {
+  auto it = container.find(key);
+  DCHECK(it != container.end());
+  container.erase(it);
+}
+
+}  // namespace
+
+////////////////////////////////////////////////////////////////////////////////
+// Public methods
+
+// static
+KeepAliveRegistry* KeepAliveRegistry::GetInstance() {
+  return base::Singleton<KeepAliveRegistry>::get();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Private methods
+
+KeepAliveRegistry::KeepAliveRegistry() {}
+
+KeepAliveRegistry::~KeepAliveRegistry() {
+  DCHECK_EQ(0u, registered_keep_alives_.size());
+}
+
+void KeepAliveRegistry::Register(const KeepAliveOptions* option) {
+  registered_keep_alives_.insert(option);
+
+  // TODO(dgn): We currently use the plain KeepAliveCount. We will integrate
+  // that in this class progressively as mechanisms are merged.
+  if (registered_keep_alives_.size() == 1)
+    chrome::IncrementKeepAliveCount();
+}
+
+void KeepAliveRegistry::Unregister(const KeepAliveOptions* option) {
+  RemoveOne(option, registered_keep_alives_);
+
+
+  // TODO(dgn): We currently use the plain KeepAliveCount. We will integrate
+  // that in this class progressively as mechanisms are merged.
+  if (registered_keep_alives_.size() == 0)
+    chrome::DecrementKeepAliveCount();
+}