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

ios/chrome/browser/ui/toolbar/toolbar_model_impl_ios_unittest.mm

Index: ios/chrome/browser/ui/toolbar/toolbar_model_impl_ios_unittest.mm
diff --git a/ios/chrome/browser/ui/toolbar/toolbar_model_impl_ios_unittest.mm b/ios/chrome/browser/ui/toolbar/toolbar_model_impl_ios_unittest.mm
index 80eddcb1c91a0e7f2e30715a5e84fe3e442b0853..91ca9bcaba936ec2e2e43460ceac49fd12a08d31 100644
--- a/ios/chrome/browser/ui/toolbar/toolbar_model_impl_ios_unittest.mm
+++ b/ios/chrome/browser/ui/toolbar/toolbar_model_impl_ios_unittest.mm
@@ -6,7 +6,6 @@
 
 #include <memory>
 
-#include "base/mac/scoped_nsobject.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
@@ -31,6 +30,10 @@
 #include "third_party/ocmock/gtest_support.h"
 #include "third_party/ocmock/ocmock_extensions.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 static const char kWebUrl[] = "http://www.chromium.org";