Adding a histrogram to track account missmatch for signin reauth.

chrome/browser/ui/sync/signin_histogram.h

+// Copyright (c) 2012 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 CHROME_BROWSER_UI_SYNC_SIGNIN_HISTOGRAM_H_
+#define CHROME_BROWSER_UI_SYNC_SIGNIN_HISTOGRAM_H_
+
+namespace signin {
+
+// Enum values used for use with the "Signin.Reauth" histogram.
+enum account_reauth{
+  // The user gave the wrong email when doing a reauth.
+  HISTOGRAM_ACCOUNT_MISSMATCH,
+
+  // The user given a reauth login screen.
+  HISTOGRAM_SHOWN,
+
+  HISTOGRAM_MAX
+};
+
+}
+
+#endif  // CHROME_BROWSER_UI_SYNC_SIGNIN_HISTOGRAM_H_