Fix ios_chrome_unittests to crash on DCHECK failure.

ios/chrome/browser/crash_loop_detection_util.h

Index: ios/chrome/browser/crash_loop_detection_util.h
diff --git a/ios/chrome/browser/crash_loop_detection_util.h b/ios/chrome/browser/crash_loop_detection_util.h
index 0d8118ba81c7b922af8c5e07175e7fb89774fce3..ec8692fb3ec71a34b7f1af2423ff327431763cc2 100644
--- a/ios/chrome/browser/crash_loop_detection_util.h
+++ b/ios/chrome/browser/crash_loop_detection_util.h
@@ -25,6 +25,9 @@ void IncrementFailedStartupAttemptCount(bool flush_immediately);
 // 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_