Metrics logging for user engagement of the Reload and Feedback buttons

ui/base/ui_metrics_types.h

+// Copyright 2017 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 UI_BASE_UI_METRICS_TYPES_H_
+#define UI_BASE_UI_METRICS_TYPES_H_
+
+namespace ui {
+// An enum for reporting interaction events to a UMA histogram.
+enum class SadTabEvent {
+  // Records that the Sad Tab was displayed.
+  SAD_TAB_EVENT_DISPLAYED = 0,
+  // Records that the main Sad Tab button was triggered.
+  SAD_TAB_EVENT_BUTTON_CLICKED,

[Eugene But (OOO till 7-30), 2017/05/16 23:49:33]

nit: It is better to initialize every enum item, because they are meant to be
stable and always correctly map to xml

[PL, 2017/05/23 23:06:38]

Done!

+  // Records that the Sad Tab help link was triggered.
+  SAD_TAB_EVENT_HELP_LINK_CLICKED,
+  // Enum end marker.
+  SAD_TAB_EVENT_MAX,
+};
+
+// Describes the mode of the Sad Tab as being in 'reload' mode.
+const char kSadTabReloadHistogramKey[] = "Tabs.SadTab.Reload.Event";
+// Describes the mode of the Sad Tab as being in 'feedback' mode.
+const char kSadTabFeedbackHistogramKey[] = "Tabs.SadTab.Feedback.Event";
+}
+
+#endif  // UI_BASE_UI_METRICS_TYPES_H_