Implement the WindowsLogoffRace finch experiment.

chrome/browser/lifetime/application_lifetime.cc

 // Copyright (c) 2012 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/application_lifetime.h"
 
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/field_trial.h"
 #include "base/prefs/pref_service.h"
 #include "base/process/kill.h"
 #include "base/process/process.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browser_process_platform_part.h"
 #include "chrome/browser/browser_shutdown.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/download/download_service.h"
 #include "chrome/browser/lifetime/browser_close_manager.h"
@@ skipping 218 matching lines @@
   // can be false in following cases. a) power-off b) signout from
   // screen locker.
   if (!AreAllBrowsersCloseable())
     browser_shutdown::OnShutdownStarting(browser_shutdown::END_SESSION);
   else
     browser_shutdown::OnShutdownStarting(browser_shutdown::BROWSER_EXIT);
   AttemptExitInternal(true);
 }
 #endif
 
+namespace {
+
+bool ExperimentUseBrokenSynchronization() {
+  const std::string group_name =
+      base::FieldTrialList::FindFullName("WindowsLogoffRace");
+  return group_name == "BrokenSynchronization";
+}
+
+}  // namespace
+
 void SessionEnding() {
   // This is a time-limited shutdown where we need to write as much to
   // disk as we can as soon as we can, and where we must kill the
   // process within a hang timeout to avoid user prompts.
 
   // Start watching for hang during shutdown, and crash it if takes too long.
   // We disarm when |shutdown_watcher| object is destroyed, which is when we
   // exit this function.
   ShutdownWatcherHelper shutdown_watcher;
   shutdown_watcher.Arm(base::TimeDelta::FromSeconds(90));
@@ skipping 11 matching lines @@
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_CLOSE_ALL_BROWSERS_REQUEST,
       content::NotificationService::AllSources(),
       content::NotificationService::NoDetails());
 
   // Write important data first.
   g_browser_process->EndSession();
 
 #if defined(OS_WIN)
   base::win::SetShouldCrashOnProcessDetach(false);
+#endif
 
-  // On Windows 7 and later, the system will consider the process ripe for
-  // termination as soon as it hides or destroys its windows. Since any
-  // execution past that point will be non-deterministically cut short, we
-  // might as well put ourselves out of that misery deterministically.
-  base::KillProcess(base::Process::Current().handle(), 0, false);
-#else
-  CloseAllBrowsers();
+  if (!ExperimentUseBrokenSynchronization()) {

[Alexei Svitkine (slow), 2014/07/14 18:55:02]

Nit: This would be easier to parse if you didn't have the negation. Either
reverse the blocks or change the function to check for the opposite with a
different name.

[Sigurður Ásgeirsson, 2014/07/14 20:31:38]

Too right, fixed.

+    // On Windows 7 and later, the system will consider the process ripe for
+    // termination as soon as it hides or destroys its windows. Since any
+    // execution past that point will be non-deterministically cut short, we
+    // might as well put ourselves out of that misery deterministically.
+    base::KillProcess(base::Process::Current().handle(), 0, false);
+  } else {
+    CloseAllBrowsers();
 
-  // Send out notification. This is used during testing so that the test harness
-  // can properly shutdown before we exit.
-  content::NotificationService::current()->Notify(
-      chrome::NOTIFICATION_SESSION_END,
-      content::NotificationService::AllSources(),
-      content::NotificationService::NoDetails());
+    // Send out notification. This is used during testing so that the test
+    // harness can properly shutdown before we exit.
+    content::NotificationService::current()->Notify(
+        chrome::NOTIFICATION_SESSION_END,
+        content::NotificationService::AllSources(),
+        content::NotificationService::NoDetails());
 
-  // This will end by terminating the process.
-  content::ImmediateShutdownAndExitProcess();
-#endif  // defined(OS_WIN)
+    // This will end by terminating the process.
+    content::ImmediateShutdownAndExitProcess();
+  }
 }
 
 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;
 }
 
@@ skipping 94 matching lines @@
   //    environment is still active.
   if (browser->host_desktop_type() == chrome::HOST_DESKTOP_TYPE_NATIVE)
     return !ash::Shell::HasInstance();
   else if (browser->host_desktop_type() == chrome::HOST_DESKTOP_TYPE_ASH)
     return BrowserList::GetInstance(chrome::HOST_DESKTOP_TYPE_NATIVE)->empty();
 #endif
   return true;
 }
 
 }  // namespace chrome