Delete old files after an update.

chrome/installer/util/delete_old_versions.h

Index: chrome/installer/util/delete_old_versions.h
diff --git a/chrome/installer/util/delete_old_versions.h b/chrome/installer/util/delete_old_versions.h
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+++ b/chrome/installer/util/delete_old_versions.h
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+// Copyright 2016 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_INSTALLER_UTIL_DELETE_OLD_VERSIONS_H_
+#define CHROME_INSTALLER_UTIL_DELETE_OLD_VERSIONS_H_
+
+namespace base {
+class FilePath;
+}
+
+namespace installer {
+
+// Deletes files that belong to old versions of Chrome. chrome.exe,
+// new_chrome.exe and their associated version directories are never deleted.
+// Also, no file is deleted for a given version if a .exe or .dll file for that
+// version is in use. Returns true if no files that belong to an old version of
+// Chrome remain.
+bool DeleteOldVersions(const base::FilePath& install_dir);
+
+}  // namespace installer
+
+#endif  // CHROME_INSTALLER_UTIL_DELETE_OLD_VERSIONS_H_