Remove factory body in *.fromEnvironment, and implement this same behavior

pkg/compiler/lib/src/js_backend/mirrors_analysis.dart

 // Copyright (c) 2016, 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.
 
 library dart2js.mirrors_handler;
 
 import '../common.dart';
 import '../common/resolution.dart';
 import '../compiler.dart';
 import '../constants/values.dart';
@@ skipping 292 matching lines @@
 
   /// Enqueue the constructor [ctor] if it is required for reflection.
   ///
   /// [enclosingWasIncluded] provides a hint whether the enclosing element was
   /// needed for reflection.
   void _enqueueReflectiveConstructor(ConstructorElement constructor,
       {bool enclosingWasIncluded}) {
     assert(constructor.isDeclaration);
     if (_shouldIncludeElementDueToMirrors(constructor,
         includedEnclosing: enclosingWasIncluded)) {
+      if (constructor.isFromEnvironmentConstructor) return;
       _logEnqueueReflectiveAction(constructor);
       ClassElement cls = constructor.enclosingClass;
       impactBuilder
           .registerTypeUse(new TypeUse.mirrorInstantiation(cls.rawType));
       impactBuilder.registerStaticUse(new StaticUse.mirrorUse(constructor));
     }
   }
 
   /// Enqueue the member [element] if it is required for reflection.
   ///
@@ skipping 153 matching lines @@
 
 /// Records that [constant] is used by the element behind [registry].
 class Dependency {
   final ConstantValue constant;
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
 
   String toString() => '$annotatedElement:${constant.toStructuredText()}';
 }