Guarantee static_method_of uses the right this (#1795)

This came up during #1760 where `Promise.resolve` must be invoked with
`this` as the `Promise` object, but we were erroneously importing it in
such a way that it didn't have a shim and `this` was `undefined`.

crates/cli-support/src/webidl/standard.rs

@@ -574,6 +574,9 @@ fn check_standard_import(import: &AuxImport) -> Result<(), Error> {
         | AuxImport::Value(AuxValue::ClassSetter(js, name)) => {
             format!("field access of `{}` for {}", name, desc_js(js))
         }
+        AuxImport::ValueWithThis(js, method) => {
+            format!("method `{}.{}`", desc_js(js), method)
+        }
         AuxImport::Instanceof(js) => format!("instance of check of {}", desc_js(js)),
         AuxImport::Static(js) => format!("static js value {}", desc_js(js)),
         AuxImport::StructuralMethod(name) => format!("structural method `{}`", name),