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

ios/chrome/browser/chrome_url_util.mm

Index: ios/chrome/browser/chrome_url_util.mm
diff --git a/ios/chrome/browser/chrome_url_util.mm b/ios/chrome/browser/chrome_url_util.mm
index 1ba6a4e36f1ff1aaaebf9cdea94ae49a2ac0ecde..fa95738b62fac273a0c1273846f599ded0ff992d 100644
--- a/ios/chrome/browser/chrome_url_util.mm
+++ b/ios/chrome/browser/chrome_url_util.mm
@@ -9,7 +9,6 @@
 #include "base/logging.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"
 #include "ios/chrome/browser/chrome_url_constants.h"
@@ -18,6 +17,10 @@
 #include "url/gurl.h"
 #include "url/url_constants.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 bool UrlIsExternalFileReference(const GURL& url) {
   return url.SchemeIs(kChromeUIScheme) &&
          base::LowerCaseEqualsASCII(url.host(), kChromeUIExternalFileHost);
@@ -43,7 +46,7 @@ bool IsHandledProtocol(const std::string& scheme) {
 }
 
 @implementation ChromeAppConstants {
-  base::scoped_nsobject<NSString> _callbackScheme;
+  NSString* _callbackScheme;
 }
 
 + (ChromeAppConstants*)sharedInstance {
@@ -64,7 +67,7 @@ bool IsHandledProtocol(const std::string& scheme) {
           base::mac::ObjCCastStrict<NSArray>(urlType[@"CFBundleURLSchemes"]);
       for (NSString* scheme in schemes) {
         if ([allowableSchemes containsObject:scheme])
-          _callbackScheme.reset([scheme copy]);
+          _callbackScheme = [scheme copy];
       }
     }
   }
@@ -73,7 +76,7 @@ bool IsHandledProtocol(const std::string& scheme) {
 }
 
 - (void)setCallbackSchemeForTesting:(NSString*)scheme {
-  _callbackScheme.reset([scheme copy]);
+  _callbackScheme = [scheme copy];
 }
 
 @end