Extend Physical Web iOS auto-enable behavior beyond first launch.

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 "components/search_engines/search_terms_data.h"
@@ skipping 41 matching lines @@
         URLHasEligibleDomain:GURL("https://www.google.com")];
 
     // Check that Google Search is configured as the default search engine.
     const TemplateURL* default_search_provider =
         ios::TemplateURLServiceFactory::GetForBrowserState(browser_state)
             ->GetDefaultSearchProvider();
     bool google_search_enabled =
         default_search_provider->IsGoogleSearchURLWithReplaceableKeyword(
             SearchTermsData());
 
-    bool auto_enable = !is_incognito && location_services_enabled &&
-                       location_authorized && geolocation_eligible &&
-                       google_search_enabled;
-
-    pref_service->SetInteger(prefs::kIosPhysicalWebEnabled,
-                             auto_enable ? physical_web::kPhysicalWebOn
-                                         : physical_web::kPhysicalWebOff);
+    if (!is_incognito && location_services_enabled && location_authorized &&
+        geolocation_eligible && google_search_enabled) {
+      pref_service->SetInteger(prefs::kIosPhysicalWebEnabled,
+                               physical_web::kPhysicalWebOn);
+    }
     preference_state = pref_service->GetInteger(prefs::kIosPhysicalWebEnabled);
   }
 
   // Scan only if the feature is enabled.
   if (preference_state == physical_web::kPhysicalWebOn) {
     GetApplicationContext()->GetPhysicalWebDataSource()->StartDiscovery(true);
   } else {
     GetApplicationContext()->GetPhysicalWebDataSource()->StopDiscovery();
   }
 }