Fix ios_chrome_unittests to crash on DCHECK failure.

ios/chrome/browser/crash_loop_detection_util.h

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_CRASH_LOOP_DETECTION_UTIL_H_
 #define IOS_CHROME_BROWSER_CRASH_LOOP_DETECTION_UTIL_H_
 
 namespace crash_util {
 
 // Returns the number of consecutive failed startups ('instant' crashes) prior
 // to this one. This method always returns the number of prior failures even
 // after calls to increment or reset the value.
 int GetFailedStartupAttemptCount();
 
 // Increases the failed startup count. This should be called immediately after
 // startup, so that if there is a crash, it is recorded.
 // If |flush_immediately| is true, the value will be persisted immediately. If
 // |flush_immediately| is false, this should be followed by a call to
 // [[NSUserDefaults standardUserDefaults] synchronize]. This is optional to
 // allow coallescing of the potentially expensive call during startup.
 void IncrementFailedStartupAttemptCount(bool flush_immediately);
 
 // Resets the failed startup count. This should be called once there is some
 // indication the user isn't in a crash loop (e.g., some amount of time has
 // elapsed, or some deliberate user action has been taken).
 void ResetFailedStartupAttemptCount();
 
+// Resets the hidden state of failed startup attempt count for testing.
+void ResetFailedStartupAttemptCountForTests();
+
 }  // namespace crash_util
 
 #endif  // IOS_CHROME_BROWSER_CRASH_LOOP_DETECTION_UTIL_H_