simplify constructors, fixes #564

test/codegen/expect/misc.js

 dart_library.library('misc', null, /* Imports */[
   'dart_sdk'
 ], function(exports, dart_sdk) {
   'use strict';
   const core = dart_sdk.core;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const misc = Object.create(null);
   misc._Uninitialized = class _Uninitialized extends core.Object {
-    _Uninitialized() {
+    new() {
     }
   };
   dart.setSignature(misc._Uninitialized, {
-    constructors: () => ({_Uninitialized: [misc._Uninitialized, []]})
+    constructors: () => ({new: [misc._Uninitialized, []]})
   });
   misc.UNINITIALIZED = dart.const(new misc._Uninitialized());
   misc.Generic$ = dart.generic(T => {
     class Generic extends core.Object {
       get type() {
         return dart.wrapType(misc.Generic);
       }
       m() {
         return core.print(dart.wrapType(T));
       }
     }
     dart.setSignature(Generic, {
       methods: () => ({m: [dart.dynamic, []]})
     });
     return Generic;
   });
   misc.Generic = misc.Generic$();
   misc.Base = class Base extends core.Object {
-    Base() {
+    new() {
       this.x = 1;
       this.y = 2;
     }
     ['=='](obj) {
       return dart.is(obj, misc.Base) && obj.x == this.x && obj.y == this.y;
     }
   };
   misc.Derived = class Derived extends core.Object {
-    Derived() {
+    new() {
       this.z = 3;
     }
     ['=='](obj) {
       return dart.is(obj, misc.Derived) && obj.z == this.z && super['=='](obj);
     }
   };
   misc._isWhitespace = function(ch) {
     return ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t';
   };
   dart.fn(misc._isWhitespace, core.bool, [core.String]);
   misc.expr = 'foo';
   misc._escapeMap = dart.const(dart.map({'\n': '\\n', '\r': '\\r', '\f': '\\f', '\b': '\\b', '\t': '\\t', '\v': '\\v', '': '\\x7F', [`\${${misc.expr}}`]: ''}));
   misc.main = function() {
     core.print(dart.toString(1));
     core.print(dart.toString(1.0));
     core.print(dart.toString(1.1));
     let x = 42;
     core.print(dart.equals(x, dart.wrapType(dart.dynamic)));
     core.print(dart.equals(x, dart.wrapType(misc.Generic)));
     core.print(new (misc.Generic$(core.int))().type);
     core.print(dart.equals(new misc.Derived(), new misc.Derived()));
     new (misc.Generic$(core.int))().m();
   };
   dart.fn(misc.main);
   // Exports:
   exports.misc = misc;
 });