Add $ before url_prefix_len to make it a variable. (#3668)
Add $ before url_prefix_len to make it a variable. (#3668)

* Add $ before url_prefix_len to make it a variable.

* Remove unnecessary string length check

* Remove useless $type_url_len

google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf,google/protobuf