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

ios/chrome/browser/web/chrome_web_client_unittest.mm

Index: ios/chrome/browser/web/chrome_web_client_unittest.mm
diff --git a/ios/chrome/browser/web/chrome_web_client_unittest.mm b/ios/chrome/browser/web/chrome_web_client_unittest.mm
index fc3763e2737ecded0cafc0b70d5ea5053e6b82b0..d98945b2a2d9c11de1cd7843efd5d521d88c9392 100644
--- a/ios/chrome/browser/web/chrome_web_client_unittest.mm
+++ b/ios/chrome/browser/web/chrome_web_client_unittest.mm
@@ -8,7 +8,6 @@
 
 #include <memory>
 
-#include "base/mac/scoped_nsobject.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/sys_string_conversions.h"
@@ -20,6 +19,10 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 // Test fixture for testing ChromeWebClient.