The project this plugin depends on, ClosureCompiler.js, is no longer maintained.
broccoli-closure-compiler
Minify JavaScript with Closure Compiler
Issues with the output or Java should be reported on the Closure Compiler issue tracker.
$ npm install --save-dev broccoli-closure-compiler
var closure-compiler = require('broccoli-closure-compiler');
tree = closure-compiler(tree, options);
See the Closure Compiler options.
MIT © Sindre Sorhus