Cleanup: Pull some browser keep alive functions into its own file.

chrome/browser/lifetime/browser_keep_alive.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 "chrome/browser/lifetime/browser_keep_alive.h"
+
+#include "base/message_loop/message_loop.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/browser_shutdown.h"
+#include "chrome/browser/lifetime/application_lifetime.h"
+#include "chrome/browser/ui/browser_finder.h"
+
+namespace browser_lifetime {
+
+namespace {
+
+int g_keep_alive_count = 0;

[sky, 2015/10/07 17:27:24]

These aren't global, they are file local. My understanding is they don't get the
g_ here. Just keep_alive_count and disable_shutdown_for_testing.

+bool g_disable_shutdown_for_testing = false;
+
+void CloseAllBrowsersIfNeeded() {
+  // If there are no browsers open and we aren't already shutting down,
+  // initiate a shutdown. Also skips shutdown if this is a unit test.
+  // (MessageLoop::current() == null or explicitly disabled).
+  if (chrome::GetTotalBrowserCount() == 0 &&
+      !browser_shutdown::IsTryingToQuit() &&
+      base::MessageLoop::current() &&
+      !g_disable_shutdown_for_testing) {
+    chrome::CloseAllBrowsers();
+  }
+}
+
+}  // namespace
+
+ScopedKeepAlive::ScopedKeepAlive() {
+  // Allow ScopedKeepAlive to be used in unit tests.
+  if (g_browser_process)
+    browser_lifetime::IncrementKeepAliveCount();
+}
+
+ScopedKeepAlive::~ScopedKeepAlive() {
+  if (g_browser_process)
+    browser_lifetime::DecrementKeepAliveCount();
+}
+
+void IncrementKeepAliveCount() {
+  // Increment the browser process refcount as long as we're keeping the
+  // application alive.
+  if (!WillKeepAlive())
+    g_browser_process->AddRefModule();
+  ++g_keep_alive_count;
+}
+
+void DecrementKeepAliveCount() {
+  DCHECK_GT(g_keep_alive_count, 0);
+  --g_keep_alive_count;
+  // Although we should have a browser process, if there is none,
+  // there is nothing to do.
+  if (!g_browser_process)
+    return;
+
+  // Allow the app to shutdown again.
+  if (!WillKeepAlive()) {
+    g_browser_process->ReleaseModule();
+    CloseAllBrowsersIfNeeded();
+  }
+}
+
+bool WillKeepAlive() {
+  return g_keep_alive_count > 0;
+}
+
+void DisableShutdownForTesting(bool disable_shutdown_for_testing) {
+  g_disable_shutdown_for_testing = disable_shutdown_for_testing;
+  if (!g_disable_shutdown_for_testing && !WillKeepAlive())
+    CloseAllBrowsersIfNeeded();
+}
+
+}  // namespace browser_lifetime