"The trend started by minifiers like UglifyJS and continued by transpilers like Babel will only accelerate." Those were predated by Closure Compiler, which was started with Gmail, and Closure Compiler in some ways still doesn't have an equal. Besides being a fully optimizing compiler, it also has a module system for code splitting, and optimization passes designed to move code at the method/property level from initia…
I believe GWT is moving on to closure for the latter optimization passes in future releases.