[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>
+
+class Profile;
+
+namespace password_manager_sync_metrics {
+
+// Returns the sync username for |profile|. Returns an empty string if the
+// |profile| isn't syncing passwords.
+std::string GetPasswordSyncUsername(Profile* profile);
+
+// Returns true if |username| and |origin| correspond to the account which is
+// syncing passwords. Will return false if |profile| is not syncing passwords.
+bool IsPasswordSyncAccountCredential(Profile* profile,
+                                     const std::string& username,
+                                     const std::string& origin);
+
+}  // namespace password_manager_sync_metrics
+
+#endif  // CHROME_BROWSER_PASSWORD_MANAGER_SYNC_METRICS_H_