Make base::Value::TYPE a scoped enum.

headless/lib/browser/devtools_api/domain_cc.template

Index: headless/lib/browser/devtools_api/domain_cc.template
diff --git a/headless/lib/browser/devtools_api/domain_cc.template b/headless/lib/browser/devtools_api/domain_cc.template
index 3345a4ad565a73e0291f7c92ed61cab543d04bc1..dc04d6e9d7bc2f7cb4a0613a6c89520055aa2564 100644
--- a/headless/lib/browser/devtools_api/domain_cc.template
+++ b/headless/lib/browser/devtools_api/domain_cc.template
@@ -103,7 +103,7 @@ void Domain::Handle{{method_name}}Response(base::Callback<void(std::unique_ptr<{
   if (callback.is_null())
     return;
   // This is an error response.
-  if (response.IsType(base::Value::TYPE_NULL)) {
+  if (response.IsType(base::Value::Type::NONE)) {
     callback.Run(nullptr);
     return;
   }