Fix "unused variable" warnings.

chrome/browser/interstitials/chrome_metrics_helper.cc

 // Copyright 2015 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 "chrome/browser/interstitials/chrome_metrics_helper.h"
 
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "components/history/core/browser/history_service.h"
@@ skipping 15 matching lines @@
     const std::string& sampling_event_name)
     : security_interstitials::MetricsHelper(
           request_url,
           settings,
           HistoryServiceFactory::GetForProfile(
               Profile::FromBrowserContext(web_contents->GetBrowserContext()),
               ServiceAccessType::EXPLICIT_ACCESS),
           g_browser_process->rappor_service()
               ? g_browser_process->rappor_service()->AsWeakPtr()
               : base::WeakPtr<rappor::RapporService>()),
+#if defined(ENABLE_CAPTIVE_PORTAL_DETECTION) || defined(ENABLE_EXTENSIONS)
       web_contents_(web_contents),
+#endif
       request_url_(request_url),
       sampling_event_name_(sampling_event_name) {
   DCHECK(!sampling_event_name_.empty());
 }
 
 ChromeMetricsHelper::~ChromeMetricsHelper() {}
 
 void ChromeMetricsHelper::StartRecordingCaptivePortalMetrics(bool overridable) {
 #if defined(ENABLE_CAPTIVE_PORTAL_DETECTION)
   captive_portal_recorder_.reset(
@@ skipping 59 matching lines @@
     case TOTAL_VISITS:
     case SET_EXTENDED_REPORTING_ENABLED:
     case SET_EXTENDED_REPORTING_DISABLED:
     case EXTENDED_REPORTING_IS_ENABLED:
     case REPORT_PHISHING_ERROR:
     case MAX_INTERACTION:
       break;
   }
 #endif
 }