Always persist histograms from setup.exe.

chrome/installer/setup/installer_metrics.h

-// 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_SETUP_INSTALLER_METRICS_H_
-#define CHROME_INSTALLER_SETUP_INSTALLER_METRICS_H_
-
-namespace base {
-class FilePath;
-}  // namespace base
-
-namespace installer {
-
-// Returns the directory in which persistent histograms will be saved. The
-// install process should create this when appropriate and remove it on
-// uninstall/rollback. If this directory does not exist when End...Storage()
-// is called then no histograms will be persisted on disk.
-base::FilePath GetPersistentHistogramStorageDir(
-    const base::FilePath& target_dir);
-
-// Creates a persistent space for any histograms that can be reported later
-// by the browser process. It should be called as early as possible in the
-// process lifetime and never called again.
-void BeginPersistentHistogramStorage();
-
-// Saves all the persistent histograms to a single file on disk for reading
-// by the browser so it can be reported. It is generally called once during
-// process exit. Multiple calls to this are possible if "snapshots" are
-// desired; they are cumulative in what is saved, not just what has changed
-// since the previous call. The |target_dir| is the install location of the
-// browser.
-void EndPersistentHistogramStorage(const base::FilePath& target_dir,
-                                   bool system_install);
-
-}  // namespace installer
-
-#endif  // CHROME_INSTALLER_SETUP_INSTALLER_METRICS_H_