Start the Physical Web scanner on Chrome start

ios/chrome/browser/physical_web/start_physical_web_discovery.mm

+// 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.
+
+#include "ios/chrome/browser/physical_web/start_physical_web_discovery.h"
+
+#import <CoreLocation/CoreLocation.h>
+
+#include "components/physical_web/data_source/physical_web_data_source.h"
+#include "ios/chrome/browser/application_context.h"
+#include "ios/chrome/browser/experimental_flags.h"
+#include "ios/chrome/browser/physical_web/physical_web_constants.h"
+#include "ios/chrome/browser/pref_names.h"
+
+void StartPhysicalWebDiscovery(PrefService* pref_service) {
+  // Do not scan if the Physical Web feature is disabled by a command line flag
+  // or Chrome Variations experiment.
+  if (!experimental_flags::IsPhysicalWebEnabled()) {
+    return;
+  }
+
+  // Do not scan for nearby devices if the user has explicitly disabled the
+  // Physical Web feature.
+  int preference_state =
+      pref_service->GetInteger(prefs::kIosPhysicalWebEnabled);
+  if (preference_state == physical_web::kPhysicalWebOff) {
+    return;
+  }
+
+  // In the default (onboarding) state, enable Physical Web scanning if the user
+  // has granted the Location app permission.
+  if (preference_state == physical_web::kPhysicalWebOnboarding) {
+    CLAuthorizationStatus auth_status = [CLLocationManager authorizationStatus];
+    if (auth_status != kCLAuthorizationStatusAuthorizedWhenInUse &&
+        auth_status != kCLAuthorizationStatusAuthorizedAlways) {
+      return;
+    }
+    pref_service->SetInteger(prefs::kIosPhysicalWebEnabled, true);
+  }
+
+  GetApplicationContext()->GetPhysicalWebDataSource()->StartDiscovery(true);
+}