Add extension event histogram values for messaging, webRequest, and webview.

extensions/browser/guest_view/guest_view_events.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 EXTENSIONS_BROWSER_GUEST_VIEW_GUEST_VIEW_EVENTS_H_
+#define EXTENSIONS_BROWSER_GUEST_VIEW_GUEST_VIEW_EVENTS_H_
+
+#include <string>
+
+#include "extensions/browser/extension_event_histogram_value.h"
+
+namespace extensions {
+namespace guest_view_events {
+
+// Returns the events::HistogramValue for the |event_name| guest view event.
+// This knows about all events for all guest view types, whether web view,
+// extension options, the guest view base class, etc.
+events::HistogramValue GetEventHistogramValue(const std::string& event_name);
+
+}  // namespace guest_view_events
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_GUEST_VIEW_GUEST_VIEW_EVENTS_H_