Introduce "CommonElements"

pkg/compiler/lib/src/js_emitter/full_emitter/emitter.dart

 // Copyright (c) 2014, 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.js_emitter.full_emitter;
 
 import 'dart:collection' show HashMap;
 import 'dart:convert';
 
 import 'package:js_runtime/shared/embedded_names.dart' as embeddedNames;
@@ skipping 2094 matching lines @@
         output.close();
       }
 
       hunkHashes[outputUnit] = hash;
     }
     return hunkHashes;
   }
 
   jsAst.Comment buildGeneratedBy() {
     List<String> options = [];
-    if (compiler.mirrorsLibrary != null) options.add('mirrors');
+    if (compiler.commonElements.mirrorsLibrary != null) options.add('mirrors');
     if (compiler.options.useContentSecurityPolicy) options.add("CSP");
     return new jsAst.Comment(generatedBy(compiler, flavor: options.join(", ")));
   }
 
   void outputSourceMap(
       CodeOutput output, LineColumnProvider lineColumnProvider, String name,
       [Uri sourceMapUri, Uri fileUri]) {
     if (!generateSourceMap) return;
     // Create a source file for the compilation output. This allows using
     // [:getLine:] to transform offsets to line numbers in [SourceMapBuilder].
@@ skipping 24 matching lines @@
     if (cachedElements.isEmpty) return;
     for (Element element in compiler.enqueuer.codegen.newlyEnqueuedElements) {
       if (element.isInstanceMember) {
         cachedClassBuilders.remove(element.enclosingClass);
 
         nativeEmitter.cachedBuilders.remove(element.enclosingClass);
       }
     }
   }
 }