Mirrors implemented via patches. 2nd try.

sdk/lib/_internal/compiler/implementation/compiler.dart

 // Copyright (c) 2012, 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;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 516 matching lines @@
     }
   }
 
   // TODO(karlklose,floitsch): move this to the javascript backend.
   /** Enable the 'JS' helper for a library if needed. */
   void maybeEnableJSHelper(LibraryElement library) {
     String libraryName = library.uri.toString();
     bool nativeTest = library.entryCompilationUnit.script.name.contains(
         'dart/tests/compiler/dart2js_native');
     if (nativeTest
-        || libraryName == 'dart:mirrors'
         || libraryName == 'dart:math'
         || libraryName == 'dart:html'
         || libraryName == 'dart:html_common'
         || libraryName == 'dart:indexed_db'
         || libraryName == 'dart:svg'
-        || libraryName == 'dart:web_audio') {
+        || libraryName == 'dart:web_audio'
+        || libraryName == 'dart:mirrors') {

[ahe, 2012/12/19 10:37:57]

Perhaps you shouldn't move this line.

       if (nativeTest
           || libraryName == 'dart:html'
           || libraryName == 'dart:html_common'
           || libraryName == 'dart:indexed_db'
-          || libraryName == 'dart:svg'
-          || libraryName == 'dart:mirrors') {
+          || libraryName == 'dart:svg') {
         // dart:html and dart:svg need access to convertDartClosureToJS and
         // annotation classes.
         // dart:mirrors needs access to the Primitives class.
         importHelperLibrary(library);
       }
       library.addToScope(
           foreignLibrary.findLocal(const SourceString('JS')), this);
       Element jsIndexingBehaviorInterface =
           findHelper(const SourceString('JavaScriptIndexingBehavior'));
       if (jsIndexingBehaviorInterface != null) {
@@ skipping 416 matching lines @@
   // TODO(johnniwinther): Use [spannable] and [message] to provide better
   // information on assertion errors.
   if (condition is Function){
     condition = condition();
   }
   if (spannable == null || !condition) {
     throw new SpannableAssertionFailure(spannable, message);
   }
   return true;
 }