dart2js: Only emit constructors of the native class interceptors that are used.

pkg/compiler/lib/src/js_emitter/old_emitter/class_emitter.dart

 // Copyright (c) 2013, 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;
 
 class ClassEmitter extends CodeEmitterHelper {
 
   ClassStubGenerator get _stubGenerator =>
       new ClassStubGenerator(compiler, namer, backend);
@@ skipping 45 matching lines @@
       jsAst.Fun function = js('function() { return this; }');
       builder.addProperty(namer.getterNameFromAccessorName(name), function);
     }
 
     emitTypeVariableReaders(classElement, builder);
 
     emitClassBuilderWithReflectionData(
         className, classElement, builder, properties);
   }
 
+  /**
+   * [emitClassConstructor] affects the generation of constructors in CSP mode.
+   */
   void emitClassConstructor(ClassElement classElement,
                             ClassBuilder builder,
                             {bool onlyForRti: false}) {
     List<String> fields = <String>[];
     if (!onlyForRti && !classElement.isNative) {
       visitFields(classElement, false,
                   (Element member,
                    String name,
                    String accessorName,
                    bool needsGetter,
@@ skipping 135 matching lines @@
         }
       });
     }
 
     if (hasMetadata) {
       builder.fieldMetadata = fieldMetadata;
     }
     return fieldsAdded;
   }
 
+  /**
+   * [emitClassGettersSetters] does not affect whether or not a class is needed

[floitsch, 2015/01/15 15:14:40]

That comment is out of context.

It should say something like:
If necessary, emits getters and setters for fields.

They can be needed in CSP mode, or in checked mode, when types need to be
verified.

[zarah, 2015/01/16 08:48:50]

You are right. Comment updated.

+   * If getters/setters are emitted, the class has fields and is therefore
+   * non-trivial.
+   */
   void emitClassGettersSetters(ClassElement classElement,
                                ClassBuilder builder,
                                {bool onlyForRti: false}) {
     if (onlyForRti) return;
 
     visitFields(classElement, false,
                 (VariableElement member,
                  String name,
                  String accessorName,
                  bool needsGetter,
@@ skipping 363 matching lines @@
           js(r'this.$builtinTypeInfo && this.$builtinTypeInfo[#]', index);
     }
     jsAst.Expression convertRtiToRuntimeType = emitter
         .staticFunctionAccess(backend.findHelper('convertRtiToRuntimeType'));
     compiler.dumpInfoTask.registerElementAst(element,
         builder.addProperty(name,
             js('function () { return #(#) }',
                 [convertRtiToRuntimeType, computeTypeVariable])));
   }
 }