[chromeos] Fix Logout automation when no browser windows are present.

chrome/browser/automation/testing_automation_provider_chromeos.cc

Index: chrome/browser/automation/testing_automation_provider_chromeos.cc
diff --git a/chrome/browser/automation/testing_automation_provider_chromeos.cc b/chrome/browser/automation/testing_automation_provider_chromeos.cc
index 960da57c5163aafc153b8060a29c85c28f8df626..b33db37194cd272b3b2cd931006d744aae23b537 100644
--- a/chrome/browser/automation/testing_automation_provider_chromeos.cc
+++ b/chrome/browser/automation/testing_automation_provider_chromeos.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/automation/testing_automation_provider.h"
 
+#include "ash/shell.h"
+#include "ash/system/tray/system_tray_delegate.h"
 #include "base/command_line.h"
 #include "base/i18n/time_formatting.h"
 #include "base/stringprintf.h"
@@ -298,6 +300,16 @@ void TestingAutomationProvider::AddLoginEventObserver(
   reply.SendSuccess(&return_value);
 }
 
+void TestingAutomationProvider::SignOut(DictionaryValue* args,
+                                        IPC::Message* reply_message) {
+  ash::Shell::GetInstance()->tray_delegate()->SignOut();
+  // Sign out has the side effect of restarting the session_manager
+  // and chrome, thereby severing the automation channel, so it's
+  // not really necessary to send a reply back. The next line is
+  // for consistency with other methods.
+  AutomationJSONReply(this, reply_message).SendSuccess(NULL);
+}
+
 void TestingAutomationProvider::LockScreen(DictionaryValue* args,
                                            IPC::Message* reply_message) {
   new ScreenLockUnlockObserver(this, reply_message, true);