old_contents: /*
  	MIT License http://www.opensource.org/licenses/mit-license.php
  	Author Tobias Koppers @sokra
  */
  var LoaderDependency = require("./LoaderDependency");
  
  function LoaderPlugin() {}
  module.exports = LoaderPlugin;
  
  LoaderPlugin.prototype.apply = function(compiler) {
  	compiler.plugin("compilation", function(compilation, params) {
  		var normalModuleFactory = params.normalModuleFactory;
  
  		compilation.dependencyFactories.set(LoaderDependency, normalModuleFactory);
  	});
  	compiler.plugin("compilation", function(compilation) {
  		compilation.plugin("normal-module-loader", function(loaderContext, module) {
  			loaderContext.loadModule = function loadModule(request, callback) {
  				var dep = new LoaderDependency(request);
  				dep.loc = request;
  				compilation.addModuleDependencies(module, [
  					[dep]
  				], true, "lm", false, function(err) {
  					if(err) return callback(err);
  
  					if(!dep.module) return callback(new Error("Cannot load the module"));
  					if(dep.module.building) dep.module.building.push(next);
  					else next();
  
  					function next(err) {
  						if(err) return callback(err);
  
  						if(dep.module.error) return callback(dep.module.error);
  						if(!dep.module._source) throw new Error("The module created for a LoaderDependency must have a property _source");
  						var source, map;
  						var moduleSource = dep.module._source;
  						if(moduleSource.sourceAndMap) {
  							var sourceAndMap = moduleSource.sourceAndMap();
  							map = sourceAndMap.map;
  							source = sourceAndMap.source;
  						} else {
  							map = moduleSource.map();
  							source = moduleSource.source();
  						}
  						if(dep.module.fileDependencies) {
  							dep.module.fileDependencies.forEach(function(dep) {
  								loaderContext.addDependency(dep);
  							});
  						}
  						if(dep.module.contextDependencies) {
  							dep.module.contextDependencies.forEach(function(dep) {
  								loaderContext.addContextDependency(dep);
  							});
  						}
  						return callback(null, source, map, dep.module);
  					}
  				});
  			};
  		});
  	});
  };
  
new_contents: /*
  	MIT License http://www.opensource.org/licenses/mit-license.php
  	Author Tobias Koppers @sokra
  */
  "use strict";
  
  const LoaderDependency = require("./LoaderDependency");
  
  class LoaderPlugin {
  
  	apply(compiler) {
  		compiler.plugin("compilation", (compilation, params) => {
  			const normalModuleFactory = params.normalModuleFactory;
  
  			compilation.dependencyFactories.set(LoaderDependency, normalModuleFactory);
  		});
  		compiler.plugin("compilation", (compilation) => {
  			compilation.plugin("normal-module-loader", (loaderContext, module) => {
  				loaderContext.loadModule = function loadModule(request, callback) {
  					const dep = new LoaderDependency(request);
  					dep.loc = request;
  					compilation.addModuleDependencies(module, [
  						[dep]
  					], true, "lm", false, (err) => {
  						if(err) return callback(err);
  
  						if(!dep.module) return callback(new Error("Cannot load the module"));
  						if(dep.module.building) dep.module.building.push(next);
  						else next();
  
  						function next(err) {
  							if(err) return callback(err);
  
  							if(dep.module.error) return callback(dep.module.error);
  							if(!dep.module._source) throw new Error("The module created for a LoaderDependency must have a property _source");
  							let source, map;
  							const moduleSource = dep.module._source;
  							if(moduleSource.sourceAndMap) {
  								const sourceAndMap = moduleSource.sourceAndMap();
  								map = sourceAndMap.map;
  								source = sourceAndMap.source;
  							} else {
  								map = moduleSource.map();
  								source = moduleSource.source();
  							}
  							if(dep.module.fileDependencies) {
  								dep.module.fileDependencies.forEach((dep) => loaderContext.addDependency(dep));
  							}
  							if(dep.module.contextDependencies) {
  								dep.module.contextDependencies.forEach((dep) => loaderContext.addContextDependency(dep));
  							}
  							return callback(null, source, map, dep.module);
  						}
  					});
  				};
  			});
  		});
  	}
  }
  module.exports = LoaderPlugin;
  
subject: upgrade LoaderPlugin to ES6