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"
+
+namespace {
+
+// Helper function to remove one token from the multisets.
+void RemoveOne(const std::string& key, std::multiset<std::string>& container) {
+  auto it = container.find(key);
+  DCHECK(it != container.end());
+  container.erase(it);
+}
+
+}  // namespace
+
+// static
+KeepAliveRegistry* KeepAliveRegistry::GetInstance() {
+  return base::Singleton<KeepAliveRegistry>::get();
+}
+
+KeepAliveRegistry::KeepAliveRegistry() {}

[sky, 2016/02/19 21:02:49]

nit: make declaration/definition order match (see style guide).

[dgn, 2016/02/22 18:01:19]

Done.

+
+KeepAliveRegistry::~KeepAliveRegistry() {
+  DCHECK_EQ(0u, registered_tokens_.size());
+}
+
+void KeepAliveRegistry::RegisterToken(const std::string& token) {
+  DCHECK(!token.empty());
+
+  registered_tokens_.insert(token);
+
+  // TODO(dgn): We currently use the plain KeepAliveCount. We will integrate
+  // that in this class progressively as mechanisms are merged.
+  if (registered_tokens_.size() == 1)
+    chrome::IncrementKeepAliveCount();
+}
+
+void KeepAliveRegistry::UnregisterToken(const std::string& token) {
+  RemoveOne(token, registered_tokens_);
+
+  // TODO(dgn): We currently use the plain KeepAliveCount. We will integrate
+  // that in this class progressively as mechanisms are merged.
+  if (registered_tokens_.size() == 0)
+    chrome::DecrementKeepAliveCount();
+}