Record the initial state of the Physical Web at startup

ios/chrome/browser/physical_web/physical_web_preference_manager.mm

Index: ios/chrome/browser/physical_web/physical_web_preference_manager.mm
diff --git a/ios/chrome/browser/physical_web/physical_web_preference_manager.mm b/ios/chrome/browser/physical_web/physical_web_preference_manager.mm
new file mode 100644
index 0000000000000000000000000000000000000000..5bbd0a22281658ad1f085fa96916cd0e7538c367
--- /dev/null
+++ b/ios/chrome/browser/physical_web/physical_web_preference_manager.mm
@@ -0,0 +1,18 @@
+// 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.
+
+#import "ios/chrome/browser/physical_web/physical_web_preference_manager.h"
+
+#include "components/prefs/pref_registry_simple.h"
+#include "ios/chrome/browser/physical_web/physical_web_constants.h"
+#include "ios/chrome/browser/pref_names.h"
+
+@implementation PhysicalWebPreferenceManager
+
++ (void)registerLocalState:(PrefRegistrySimple*)registry {
+  registry->RegisterIntegerPref(prefs::kIosPhysicalWebEnabled,
+                                physical_web::kPhysicalWebOnboarding);
+}
+
+@end