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

ios/chrome/browser/ui/contextual_search/js_contextual_search_manager.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/ui/contextual_search/js_contextual_search_manager.h"
 
 #include "base/ios/ios_util.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_block.h"
-#include "base/mac/scoped_nsobject.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 static NSString* const kEnableSelectionChangeListener =
     @"__gCrWeb.contextualSearch.enableSelectionChangeListener(%@);";
 
 static NSString* const kSetMutationObserverDelay =
     @"__gCrWeb.contextualSearch.setMutationObserverDelay(%f);";
 
 static NSString* const kDisableMutationObserver =
     @"__gCrWeb.contextualSearch.disableMutationObserver();";
 
 static NSString* const kSetBodyTouchListenerDelay =
@@ skipping 82 matching lines @@
                    completionHandler:(web::JavaScriptResultBlock)completion {
   if (startOffset < 0 || endOffset < 0)
     return;
   NSString* expandHightlightString =
       [NSString stringWithFormat:kExpandHighlight, startOffset, endOffset];
 
   [self executeJavaScript:expandHightlightString completionHandler:completion];
 }
 
 @end