Suboptimal minification for object methods for ECMASCRIPT6 mode

[MaxGraey]

Example for https://closure-compiler.appspot.com:

// ==ClosureCompiler==
// @compilation_level SIMPLE_OPTIMIZATIONS
// @language_in ECMASCRIPT6 
// @language_out ECMASCRIPT6
// @output_file_name default.js
// @formatting pretty_print
// ==/ClosureCompiler==

this['stringview_iter'] = {
  'pop'() {
     return Module['_BinaryenPop'](module, Module['stringview_iter']);
  }
};

Simple / Advanced optimization (with pretty printing):

'use strict';
this.stringview_iter = {pop:function() {
  return Module._BinaryenPop(module, Module.stringview_iter);
}};

Expected:

'use strict';
this.stringview_iter = {pop() {
  return Module._BinaryenPop(module, Module.stringview_iter);
}};