Add WebAPK installation metrics.

chrome/browser/android/webapk/webapk_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_BROWSER_ANDROID_WEBAPK_WEBAPK_METRICS_H_
+#define CHROME_BROWSER_ANDROID_WEBAPK_WEBAPK_METRICS_H_
+
+namespace webapk {
+
+// Keep these enums up to date with tools/metrics/histograms/histograms.xml.
+// Events for WebAPKs installation flow. The sum of |InstalllEvent| histogram

[dominickn, 2016/09/21 21:56:17]

Nit: InstallEvent

+// is the total number of times that a WebAPK infobar was triggered.
+enum InstallEvent {
+  // The user did not interact with the infobar.
+  INFOBAR_IGNORED,
+  // The infobar with the "Add-to-Homescreen" button is dismissed before the
+  // installation started. "Dismiss" means the user closes the infobar by
+  // clicking the "X" button.
+  INFOBAR_DISMISSED_BEFORE_INSTALLATION,
+  // The infobar with the "Adding" button is dismissed during installation.
+  INFOBAR_DISMISSED_DURING_INSTALLATION,
+  INSTALL_COMPLETED,
+  INSTALL_FAILED,
+  INSTALL_EVENT_MAX,
+};
+
+// The ways in which WebAPK installation can be started.
+enum InstallSource {
+  INSTALL_SOURCE_BANNER,
+  INSTALL_SOURCE_MENU,
+  INSTALL_SOURCE_MAX,
+};
+
+// The ways in which WebApk installation can be triggered.

[dominickn, 2016/09/21 21:56:16]

Nit: The ways in which the WebAPK infobar can be shown.

+enum InfoBarShown {
+  WEBAPK_INFOBAR_SHOWN_FROM_BANNER,
+  WEBAPK_INFOBAR_SHOWN_FROM_MENU,
+  WEBAPK_INFOBAR_SHOWN_MAX,
+};
+
+// User actions after a WebAPK is installed.
+enum UserAction {
+  // TODO(hanxi|zpeng): Records the first two user actions after
+  // crbug.com/638614 is fixed.
+  // Launch a previously installed WebAPK since the WebAPK has been installed on
+  // the device before.
+  USER_ACTION_OPEN,
+  USER_ACTION_OPEN_DISMISS,
+  // Open a newly installed WebAPK via a successful installation.
+  USER_ACTION_INSTALLED_OPEN,
+  USER_ACTION_INSTALLED_OPEN_DISMISS,
+  USER_ACTION_MAX,
+};
+
+void TrackInstallEvent(InstallEvent event);
+void TrackInstallSource(InstallSource event);
+void TrackInstallInfoBarShown(InfoBarShown event);
+void TrackUserAction(UserAction event);
+
+};  // namespace webapk
+
+#endif  // CHROME_BROWSER_ANDROID_WEBAPK_WEBAPK_METRICS_H_