Persist setup metrics and have Chrome report them during UMA upload.

chrome/installer/setup/installer_metrics.h

Index: chrome/installer/setup/installer_metrics.h
diff --git a/chrome/installer/setup/installer_metrics.h b/chrome/installer/setup/installer_metrics.h
new file mode 100644
index 0000000000000000000000000000000000000000..7510b984c4b336a8b477bf1204c3ab191f48e7ae
--- /dev/null
+++ b/chrome/installer/setup/installer_metrics.h
@@ -0,0 +1,25 @@
+// 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 {
+
+// Creates a persistent space for any histograms that can be reported later
+// by the browser process.
+void BeginPersistentHistogramStorage();
+
+// Saves all the persistent histograms to a single file on disk for reading
+// by the browser so it can be reported.

[Alexei Svitkine (slow), 2016/02/19 18:16:40]

Nit: Can you expand the comment to indicate whether it's an error to call this
multiple times? Or is it valid if you have pairs of Begin() and End() calls?

The naming scheme implies that the latter might be supported, but looking at the
code, I'm not so sure.

[bcwhite, 2016/02/19 19:50:14]

Done.

+void EndPersistentHistogramStorage(const base::FilePath& target_dir);
+
+}  // namespace installer
+
+#endif  // CHROME_INSTALLER_SETUP_INSTALLER_METRICS_H_
+