Move mod_pagespeed metrics out of prerender.

chrome/browser/mod_pagespeed/mod_pagespeed_metrics.h

+// Copyright 2015 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_MOD_PAGESPEED_MOD_PAGESPEED_METRICS_H_
+#define CHROME_BROWSER_MOD_PAGESPEED_MOD_PAGESPEED_METRICS_H_
+
+#include "content/public/common/resource_type.h"
+
+class GURL;
+
+namespace net {
+class HttpResponseHeaders;
+}
+
+namespace mod_pagespeed {
+
+// Records metrics about mod_pagespeed headers.
+//
+// See
+// https://developers.google.com/speed/pagespeed/module/configuration#XHeaderValue
+void RecordMetrics(const content::ResourceType resource_type,
+                   const GURL& request_url,
+                   const net::HttpResponseHeaders* response_headers);
+
+}  // namespace mod_pagespeed
+
+#endif  // CHROME_BROWSER_MOD_PAGESPEED_MOD_PAGESPEED_METRICS_H_