Implement the WindowsLogoffRace finch experiment.

chrome/browser/lifetime/application_lifetime.cc

Index: chrome/browser/lifetime/application_lifetime.cc
diff --git a/chrome/browser/lifetime/application_lifetime.cc b/chrome/browser/lifetime/application_lifetime.cc
index 21b9e3bda36e273f8b1bb21e662c098a55279e8c..38eaa56ceab8b01fd4740e33b29d61bfe65ad98c 100644
--- a/chrome/browser/lifetime/application_lifetime.cc
+++ b/chrome/browser/lifetime/application_lifetime.cc
@@ -11,6 +11,7 @@
 #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"
@@ -249,6 +250,16 @@ void ExitCleanly() {
 }
 #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
@@ -280,25 +291,27 @@ void SessionEnding() {
 
 #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() {