ios: Compare user defaults to pref for save shutdown beacon.

There is some speculation that local state is not persisting properly
in some cases.  Add a histogram to also set the value in NSUserDefaults
and to compare those two values.

Bug: 1161529

Change-Id: I67f4caf8060f037151dcc6653825ec17b556dee6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611966Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Mohammad Refaat <mrefaat@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841071}

ios/chrome/browser/application_context_impl.mm

@@ -14,6 +14,7 @@
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/path_service.h"
 #include "base/sequenced_task_runner.h"
 #include "base/strings/sys_string_conversions.h"
@@ -111,6 +112,17 @@ void BindNetworkChangeManagerReceiver(
   network_change_manager->AddReceiver(std::move(receiver));
 }
 
+// Used to enable the workaround for a local state not persisting sometimes.
+NSString* const kLastSessionExitedCleanly = @"LastSessionExitedCleanly";
+
+// Set both local_state and user defaults kLastSessionExitedCleanly to |clean|.
+void SetLastSessionExitedCleanly(PrefService* local_state, bool clean) {
+  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
+  [defaults setBool:clean forKey:kLastSessionExitedCleanly];
+  [defaults synchronize];
+  local_state->SetBoolean(prefs::kLastSessionExitedCleanly, clean);
+}
+
 }  // namespace
 
 ApplicationContextImpl::ApplicationContextImpl(
@@ -233,7 +245,7 @@ void ApplicationContextImpl::OnAppEnterForeground() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   PrefService* local_state = GetLocalState();
-  local_state->SetBoolean(prefs::kLastSessionExitedCleanly, false);
+  SetLastSessionExitedCleanly(local_state, false);
 
   // Tell the metrics services that the application resumes.
   metrics::MetricsService* metrics_service = GetMetricsService();
@@ -267,7 +279,7 @@ void ApplicationContextImpl::OnAppEnterBackground() {
   }
 
   PrefService* local_state = GetLocalState();
-  local_state->SetBoolean(prefs::kLastSessionExitedCleanly, true);
+  SetLastSessionExitedCleanly(local_state, true);
 
   // Tell the metrics services they were cleanly shutdown.
   metrics::MetricsService* metrics_service = GetMetricsService();
@@ -520,6 +532,37 @@ void ApplicationContextImpl::CreateLocalState() {
     was_last_shutdown_clean_ =
         local_state_->GetBoolean(prefs::kLastSessionExitedCleanly);
   }
+
+  // The logic below mirrors clean_exit_beacon.  For historical reasons ios/
+  // does not use this beacon directly.  This code should be merged with clean
+  // exit beacon (as long as the user default workaround can also go into the
+  // clean exit beacon).
+
+  // An enumeration of all possible permutations of the the beacon state in the
+  // registry and in Local State.
+  enum {
+    DIRTY_DIRTY,
+    DIRTY_CLEAN,
+    CLEAN_DIRTY,
+    CLEAN_CLEAN,
+    MISSING_DIRTY,
+    MISSING_CLEAN,
+    NUM_CONSISTENCY_ENUMS
+  } consistency = DIRTY_DIRTY;
+  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
+  if ([defaults objectForKey:kLastSessionExitedCleanly] != nil) {
+    bool user_defaults_was_last_shutdown_clean_ =
+        [defaults boolForKey:kLastSessionExitedCleanly];
+    if (user_defaults_was_last_shutdown_clean_) {
+      consistency = was_last_shutdown_clean_ ? CLEAN_CLEAN : CLEAN_DIRTY;
+    } else {
+      consistency = was_last_shutdown_clean_ ? DIRTY_CLEAN : DIRTY_DIRTY;
+    }
+  } else {
+    consistency = was_last_shutdown_clean_ ? MISSING_CLEAN : MISSING_DIRTY;
+  }
+  base::UmaHistogramEnumeration("UMA.CleanExitBeaconConsistency", consistency,
+                                NUM_CONSISTENCY_ENUMS);
 }
 
 void ApplicationContextImpl::CreateGCMDriver() {