Add BackgroundModeOptimizer that can restart the browser

chrome/browser/browser_shutdown.cc

Index: chrome/browser/browser_shutdown.cc
diff --git a/chrome/browser/browser_shutdown.cc b/chrome/browser/browser_shutdown.cc
index b81446a2df396e80890d92efd58908abc00cbeab..90ceca86154e980f6ed566d2e87b5517367323f4 100644
--- a/chrome/browser/browser_shutdown.cc
+++ b/chrome/browser/browser_shutdown.cc
@@ -69,6 +69,10 @@ namespace {
 // Whether the browser is trying to quit (e.g., Quit chosen from menu).
 bool g_trying_to_quit = false;
 
+// If restarting and this is true then add the kNoStartupWindow switch to the
+// command line.
+bool g_should_restart_in_background = false;
+
 Time* g_shutdown_started = nullptr;
 ShutdownType g_shutdown_type = NOT_VALID;
 int g_shutdown_num_processes;
@@ -239,6 +243,8 @@ void ShutdownPostThreadsStop(bool restart_last_session) {
       else
         new_cl->AppendSwitch(it.first);
     }
+    if (g_should_restart_in_background)

[sky, 2016/05/18 19:23:06]

Having a global is error prone. Can you make this a parameter to this function?

[dgn, 2016/06/20 17:45:19]

Done. It made it a static class member in BackgroundModeManager. Sadly I
couldn't make it instance member because the BMM gets cleared by the time we
want to read the value.

+      new_cl->AppendSwitch(switches::kNoStartupWindow);
 
 #if defined(OS_POSIX) || defined(OS_WIN)
     upgrade_util::RelaunchChromeBrowser(*new_cl.get());
@@ -335,6 +341,10 @@ bool IsTryingToQuit() {
   return g_trying_to_quit;
 }
 
+void SetShouldRestartInBackground(bool should_restart_in_background) {
+  g_should_restart_in_background = should_restart_in_background;
+}
+
 void StartShutdownTracing() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();