[Extensions Bindings] Add a bridge to use current custom bindings

extensions/renderer/argument_spec.cc

Index: extensions/renderer/argument_spec.cc
diff --git a/extensions/renderer/argument_spec.cc b/extensions/renderer/argument_spec.cc
index f79ea8a9107f44cd2d1da2e4a275ba82ba7cac67..50b91a7217e3a7e45b7f9aed37157424e0efc28b 100644
--- a/extensions/renderer/argument_spec.cc
+++ b/extensions/renderer/argument_spec.cc
@@ -47,6 +47,15 @@ void ArgumentSpec::InitializeType(const base::DictionaryValue* dict) {
     return;
   }
 
+  {
+    const base::ListValue* choices = nullptr;
+    if (dict->GetList("choices", &choices)) {
+      // TODO(devlin): Properly handle choices.
+      type_ = ArgumentType::ANY;
+      return;
+    }
+  }
+
   std::string type_string;
   CHECK(dict->GetString("type", &type_string));
   if (type_string == "integer")