Allow the app banner installability check to run on page load.

chrome/browser/installable/installable_metrics.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 CHROME_BROWSER_INSTALLABLE_INSTALLABLE_METRICS_H_
+#define CHROME_BROWSER_INSTALLABLE_INSTALLABLE_METRICS_H_
+
+// This enum backs a UMA histogram and must be treated as append-only.
+enum class InstallabilityCheckStatus {
+  NOT_STARTED,
+  STOPPED_BEFORE_COMPLETION,
+  IN_PROGRESS_NON_PROGRESSIVE_WEB_APP,
+  IN_PROGRESS_PROGRESSIVE_WEB_APP,
+  COMPLETE_NON_PROGRESSIVE_WEB_APP,
+  COMPLETE_PROGRESSIVE_WEB_APP,
+  COUNT,
+};
+
+class InstallableMetrics {
+ public:
+  static void RecordMenuOpenHistogram(InstallabilityCheckStatus status);
+  static void RecordMenuItemAddToHomescreenHistogram(
+      InstallabilityCheckStatus status);
+};
+
+#endif  // CHROME_BROWSER_INSTALLABLE_INSTALLABLE_METRICS_H_