[ObjC ARC] Converts ios/chrome/browser/ui/contextual_search:contextual_search to ARC.

ios/chrome/browser/ui/contextual_search/contextual_search_metrics.mm

 // Copyright 2014 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/ui/contextual_search/contextual_search_metrics.h"
 
 #include <map>
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/user_metrics.h"
 #include "base/time/time.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using ContextualSearch::PanelState;
 using ContextualSearch::StateChangeReason;
 
 // TODO(crbug.com/546238): Convert this into a class that is injected into
 // CSController so it can be mocked and tested.
 
 #define VLOG_UMA_HISTOGRAM_ENUMERATION(log_level, name, sample) \
   DVLOG(log_level) << (name) << ": " << (sample);
 
 #define VLOG_UMA_HISTOGRAM_TIMES(log_level, name, sample) \
@@ skipping 759 matching lines @@
                              EXIT_MAXIMIZED_TO_OTHER),
           EXIT_MAXIMIZED_TO_COUNT, 1);
       break;
     default:
       NOTREACHED() << "RecordFirstStateExit for unexpected state " << to_state;
       break;
   }
 }
 
 }  // namespace ContextualSearch