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/lifetime/application_lifetime.h"
+#include "chrome/browser/lifetime/keep_alive_types.h"
+
+namespace {
+
+KeepAliveRegistry* g_test_instance = nullptr;
+
+}  // namespace
+
+////////////////////////////////////////////////////////////////////////////////
+// Public methods
+
+// static
+KeepAliveRegistry* KeepAliveRegistry::GetInstance() {
+  if (g_test_instance)
+    return g_test_instance;
+
+  return base::Singleton<KeepAliveRegistry>::get();
+}
+
+bool KeepAliveRegistry::WillKeepAlive() const {
+  return registered_count_ > 0;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Private methods
+
+KeepAliveRegistry::KeepAliveRegistry() {}
+
+KeepAliveRegistry::~KeepAliveRegistry() {
+  DCHECK_EQ(0, registered_count_);
+}
+
+// static
+void KeepAliveRegistry::SetInstanceForTesting(KeepAliveRegistry* new_instance) {
+  g_test_instance = new_instance;
+}
+
+void KeepAliveRegistry::Register(KeepAliveOrigin origin) {
+  if (!WillKeepAlive())
+    HugBrowser();
+
+  ++registered_keep_alives_[origin];
+  ++registered_count_;
+}
+
+void KeepAliveRegistry::Unregister(KeepAliveOrigin origin) {
+  --registered_count_;
+  --registered_keep_alives_[origin];

[sky, 2016/02/25 00:25:18]

remove from rendered_keep_alives if count == 0

[dgn, 2016/02/25 17:19:46]

Done.

+  DCHECK_GE(registered_count_, 0);
+  DCHECK_GE(registered_keep_alives_[origin], 0);
+
+  if (!WillKeepAlive())
+    ReleaseBrowser();
+}
+
+void KeepAliveRegistry::HugBrowser() {
+  // TODO(dgn): We currently use the plain KeepAliveCount. We will integrate
+  // that in this class progressively as mechanisms are merged.
+  chrome::IncrementKeepAliveCount();
+}
+
+void KeepAliveRegistry::ReleaseBrowser() {
+  // TODO(dgn): We currently use the plain KeepAliveCount. We will integrate
+  // that in this class progressively as mechanisms are merged.
+  chrome::DecrementKeepAliveCount();
+}