[Password Manager] Add UMA stats to track interaction with synced accounts.

chrome/browser/password_manager/sync_metrics.h

+// Copyright 2014 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_PASSWORD_MANAGER_SYNC_METRICS_H_
+#define CHROME_BROWSER_PASSWORD_MANAGER_SYNC_METRICS_H_
+
+#include <string>
+
+#include "components/password_manager/core/common/sync_state.h"
+
+class Profile;
+
+namespace password_manager_sync_metrics {
+
+// Returns the current state of syncing as is interesting to the password
+// manager and the username of the account currently syncing, if there is one.
+// |sync_username| is unchanged if sync is not currrently enabled.
+void GetSyncUsernameAndState(Profile* profile,
+                             std::string* sync_username,
+                             password_manager::SyncState* sync_state);
+
+}  // namespace password_manager_sync_metrics
+
+#endif  // CHROME_BROWSER_PASSWORD_MANAGER_SYNC_METRICS_H_