[ObjC ARC] Converts ios/chrome/browser/crash_report to ARC

ios/chrome/browser/crash_report/crash_report_multi_parameter.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.
 
 #import "ios/chrome/browser/crash_report/crash_report_multi_parameter.h"
 
 #include <memory>
 
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/values.h"
 #import "ios/chrome/browser/crash_report/breakpad_helper.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // Maximum size of a breakpad parameter. The length of the dictionary serialized
 // into JSON cannot exceed this length. See declaration in (BreakPad.h) for
 // details.
 const int kMaximumBreakpadValueSize = 255;
 }
 
 @implementation CrashReportMultiParameter {
   base::scoped_nsobject<NSString> crashReportKey_;
   std::unique_ptr<base::DictionaryValue> dictionary_;
@@ skipping 55 matching lines @@
     return;
   }
   breakpad_helper::AddReportParameter(
       crashReportKey_,
       [NSString stringWithCString:stateAsJson.c_str()
                          encoding:[NSString defaultCStringEncoding]],
       true);
 }
 
 @end