Remove the WindowsLogoffRace experiment.

Unfortunately these are not the droids we're looking for.

BUG=388741

Review URL: https://codereview.chromium.org/783533002

Cr-Commit-Position: refs/heads/master@{#307026}

3 files changed, 7 insertions, 118 deletions

diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index 34ddec2..deb6202 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -446,25 +446,9 @@ bool RundownTaskCounter::TimedWait(const base::TimeDelta& max_time) {
   return waitable_event_.TimedWait(max_time);
 }
 
-bool ExperimentUseBrokenSynchronization() {
-  // The logoff behavior used to have a race, whereby it would perform profile
-  // IO writes on the blocking thread pool, but would sycnhronize to the FILE
-  // thread. Windows feels free to terminate any process that's hidden or
-  // destroyed all it's windows, and sometimes Chrome would be terminated
-  // with pending profile IO due to this mis-synchronization.
-  // Under the "WindowsLogoffRace" experiment group, the broken behavior is
-  // emulated, in order to allow measuring what fraction of unclean shutdowns
-  // are due to this bug.
-  const std::string group_name =
-      base::FieldTrialList::FindFullName("WindowsLogoffRace");
-  return group_name == "BrokenSynchronization";
-}
-
 }  // namespace
 
 void BrowserProcessImpl::EndSession() {
-  bool use_broken_synchronization = ExperimentUseBrokenSynchronization();
-
   // Mark all the profiles as clean.
   ProfileManager* pm = profile_manager();
   std::vector<Profile*> profiles(pm->GetLoadedProfiles());
@@ -473,8 +457,7 @@ void BrowserProcessImpl::EndSession() {
     Profile* profile = profiles[i];
     profile->SetExitType(Profile::EXIT_SESSION_ENDED);
 
-    if (!use_broken_synchronization)
-      rundown_counter->Post(profile->GetIOTaskRunner().get());
+    rundown_counter->Post(profile->GetIOTaskRunner().get());
   }
 
   // Tell the metrics service it was cleanly shutdown.
@@ -487,8 +470,7 @@ void BrowserProcessImpl::EndSession() {
     // commit metrics::prefs::kStabilitySessionEndCompleted change immediately.
     local_state()->CommitPendingWrite();
 
-    if (!use_broken_synchronization)
-      rundown_counter->Post(local_state_task_runner_.get());
+    rundown_counter->Post(local_state_task_runner_.get());
 #endif
   }
 
@@ -502,11 +484,6 @@ void BrowserProcessImpl::EndSession() {
   // If you change the condition here, be sure to also change
   // ProfileBrowserTests to match.
 #if defined(USE_X11) || defined(OS_WIN)
-  if (use_broken_synchronization) {
-    rundown_counter->Post(
-        BrowserThread::GetMessageLoopProxyForThread(BrowserThread::FILE).get());
-  }
-
   // Do a best-effort wait on the successful countdown of rundown tasks. Note
   // that if we don't complete "quickly enough", Windows will terminate our
   // process.
diff --git a/chrome/browser/lifetime/application_lifetime.cc b/chrome/browser/lifetime/application_lifetime.cc
index 5f57bd6..ddac004 100644
--- a/chrome/browser/lifetime/application_lifetime.cc
+++ b/chrome/browser/lifetime/application_lifetime.cc
@@ -11,7 +11,6 @@
 #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_handle.h"
@@ -251,16 +250,6 @@ 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
@@ -294,25 +283,11 @@ void SessionEnding() {
   base::win::SetShouldCrashOnProcessDetach(false);
 #endif
 
-  if (ExperimentUseBrokenSynchronization()) {
-    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());
-
-    // This will end by terminating the process.
-    content::ImmediateShutdownAndExitProcess();
-  } else {
-    // 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::GetCurrentProcessHandle(), 0, false);
-  }
+  // 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::GetCurrentProcessHandle(), 0, false);
 }
 
 void IncrementKeepAliveCount() {
diff --git a/chrome/browser/profiles/profile_browsertest.cc b/chrome/browser/profiles/profile_browsertest.cc
index e5eeffd..5a43b75 100644
--- a/chrome/browser/profiles/profile_browsertest.cc
+++ b/chrome/browser/profiles/profile_browsertest.cc
@@ -8,7 +8,6 @@
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/json/json_reader.h"
-#include "base/metrics/field_trial.h"
 #include "base/prefs/pref_service.h"
 #include "base/sequenced_task_runner.h"
 #include "base/synchronization/waitable_event.h"
@@ -398,66 +397,4 @@ IN_PROC_BROWSER_TEST_F(ProfileBrowserTest,
   ASSERT_TRUE(succeeded) << "profile->EndSession() timed out too often.";
 }
 
-IN_PROC_BROWSER_TEST_F(ProfileBrowserTest,
-                       EndSessionBrokenSynchronizationExperiment) {
-  base::ScopedTempDir temp_dir;
-  ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
-
-  // Select into the field trial group.
-  base::FieldTrialList::CreateFieldTrial("WindowsLogoffRace",
-                                         "BrokenSynchronization");
-
-  ProfileManager* profile_manager = g_browser_process->profile_manager();
-  ASSERT_TRUE(profile_manager);
-  std::vector<Profile*> loaded_profiles = profile_manager->GetLoadedProfiles();
-
-  ASSERT_NE(loaded_profiles.size(), 0UL);
-  Profile* profile = loaded_profiles[0];
-
-  bool mis_wrote = false;
-  // This retry loop reduces flakiness due to the fact that this ultimately
-  // tests whether or not a code path hits a timed wait.
-  for (size_t retries = 0; retries < 3; ++retries) {
-    // Flush the profile data to disk for all loaded profiles.
-    profile->SetExitType(Profile::EXIT_CRASHED);
-    FlushTaskRunner(profile->GetIOTaskRunner().get());
-
-    // Make sure that the prefs file was written with the expected key/value.
-    ASSERT_EQ(GetExitTypePreferenceFromDisk(profile), "Crashed");
-
-    base::WaitableEvent is_blocked(false, false);
-    base::WaitableEvent* unblock = new base::WaitableEvent(false, false);
-
-    // Block the profile's IO thread.
-    profile->GetIOTaskRunner()->PostTask(FROM_HERE,
-        base::Bind(&BlockThread, &is_blocked, base::Owned(unblock)));
-    // Wait for the IO thread to actually be blocked.
-    is_blocked.Wait();
-
-    // The blocking wait in EndSession has a timeout, so a non-write can only be
-    // concluded if it happens in less time than the timeout.
-    base::Time start = base::Time::Now();
-
-    // With the broken synchronization this is expected to return without
-    // blocking for the Profile's IO thread.
-    g_browser_process->EndSession();
-
-    base::Time end = base::Time::Now();
-
-    // The EndSession timeout is 10 seconds, we take a 5 second run-through as
-    // sufficient proof that we didn't hit the timed wait.
-    if (end - start < base::TimeDelta::FromSeconds(5)) {
-      // Make sure that the prefs file is unmodified with the expected
-      // key/value.
-      EXPECT_EQ(GetExitTypePreferenceFromDisk(profile), "Crashed");
-      mis_wrote = true;
-    }
-
-    // Release the IO thread thread.
-    unblock->Signal();
-  }
-
-  ASSERT_TRUE(mis_wrote);
-}
-
 #endif  // defined(USE_X11) || defined(OS_WIN)