[iOS] Upstream crash loop detection utilities

ios/chrome/browser/crash_loop_detection_util.mm

+// Copyright 2013 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 "ios/chrome/browser/crash_loop_detection_util.h"
+
+#import <Foundation/Foundation.h>
+
+namespace {
+NSString* const kAppStartupFailureCountKey = @"AppStartupFailureCount";
+}
+
+namespace crash_util {
+
+int GetFailedStartupAttemptCount() {
+  static int startup_attempt_count = -1;
+  if (startup_attempt_count == -1) {
+    NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
+    startup_attempt_count = [defaults integerForKey:kAppStartupFailureCountKey];
+  }
+  return startup_attempt_count;
+}
+
+void IncrementFailedStartupAttemptCount(bool flush_immediately) {
+  int startup_attempt_count = GetFailedStartupAttemptCount();
+  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
+  [defaults setInteger:(startup_attempt_count + 1)
+                forKey:kAppStartupFailureCountKey];
+  if (flush_immediately)
+    [defaults synchronize];
+}
+
+void ResetFailedStartupAttemptCount() {
+  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
+  if ([defaults integerForKey:kAppStartupFailureCountKey] != 0) {
+    [defaults setInteger:0 forKey:kAppStartupFailureCountKey];
+    [defaults synchronize];
+  }
+}
+
+}  // namespace crash_util