[ObjC ARC] Converts ios/chrome/browser/metrics:metrics_internal to ARC.

ios/chrome/browser/metrics/new_tab_page_uma.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.
 
 #import "ios/chrome/browser/metrics/new_tab_page_uma.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "components/google/core/browser/google_util.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
 #import "ios/chrome/browser/tabs/tab.h"
 #import "ios/chrome/browser/tabs/tab_model.h"
 #import "ios/chrome/browser/tabs/tab_model_list.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace new_tab_page_uma {
 
 bool IsCurrentlyOnNTP(ios::ChromeBrowserState* browserState) {
   TabModel* tabModel = GetLastActiveTabModelForChromeBrowserState(browserState);
   return tabModel.currentTab &&
          tabModel.currentTab.url == GURL(kChromeUINewTabURL);
 }
 
 void RecordAction(ios::ChromeBrowserState* browserState, ActionType type) {
   DCHECK(browserState);
@@ skipping 14 matching lines @@
     RecordAction(browserState, ACTION_SEARCHED_USING_OMNIBOX);
   } else {
     if (google_util::IsGoogleHomePageUrl(GURL(url))) {
       RecordAction(browserState, ACTION_NAVIGATED_TO_GOOGLE_HOMEPAGE);
     } else {
       RecordAction(browserState, ACTION_NAVIGATED_USING_OMNIBOX);
     }
   }
 }
 }