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_
+
+class InstallableMetrics {
+ public:
+  // This enum backs a UMA histogram and must be treated as append-only.
+  enum InstallabilityCheckStatus {
+    NOT_STARTED,
+    IN_PROGRESS_NON_PWA,
+    IN_PROGRESS_PWA,
+    COMPLETE_NON_PWA,
+    COMPLETE_PWA,
+    MAX,
+  };
+
+  static void RecordMenuOpenHistogram(InstallabilityCheckStatus status);
+  static void RecordMenuItemAddToHomescreenHistogram(
+      InstallabilityCheckStatus status);
+};
+
+#endif  // CHROME_BROWSER_INSTALLABLE_INSTALLABLE_METRICS_H_