dart2js: Better comment for startup-emitter.

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter.startup_emitter.model_emitter;
 
 /// The fast startup emitter's goal is to minimize the amount of work that the
 /// JavaScript engine has to do before it can start running user code.
 ///
 /// Whenever possible, the emitter uses object literals instead of updating
@@ skipping 13 matching lines @@
 ///     // Inheritance is achieved by updating the prototype objects (hidden in
 ///     // a helper function):
 ///     A.Point.prototype.__proto__ = H.Object.prototype;
 ///
 /// The emitter doesn't try to be clever and emits everything beforehand. This
 /// increases the output size, but improves performance.
 ///
 // The code relies on the fact that all Dart code is inside holders. As such
 // we can use "global" names however we want. As long as we don't shadow
 // JavaScript variables (like `Array`) we are free to chose whatever variable
-// names we want. Furthermore, the minifier reduces the names of the variables.
+// names we want. Furthermore, the pretty-printer minifies local variables, thus
+// reducing their size.
 const String mainBoilerplate = '''
 {
 // Declare deferred-initializer global, which is used to keep track of the
 // loaded fragments.
 #deferredInitializer;
 
 (function() {
 // Copies the own properties from [from] to [to].
 function copyProperties(from, to) {
   var keys = Object.keys(from);
@@ skipping 222 matching lines @@
     MainFragment fragment = program.fragments.first;
     throw new UnimplementedError('emitMain');
   }
 
   js.Statement emitDeferredFragment(DeferredFragment fragment,
                                     js.Expression deferredTypes,
                                     List<Holder> holders) {
     throw new UnimplementedError('emitDeferred');
   }
 }