dart2Js: bailout early when using the new emitter with mirrors.

pkg/compiler/lib/src/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 1304 matching lines @@
           }
 
           chainCount++;
           if (chainCount > chainLimit) {
             // Assume there are more import chains.
             importChains.add('...');
             return false;
           }
           return true;
         });
-        reportWarning(NO_LOCATION_SPANNABLE,
-            MessageKind.IMPORT_EXPERIMENTAL_MIRRORS,
-            {'importChain': importChains.join(
-                 MessageKind.IMPORT_EXPERIMENTAL_MIRRORS_PADDING)});
+
+        if (const bool.fromEnvironment("dart2js.use.new.emitter")) {
+          reportError(NO_LOCATION_SPANNABLE,
+                      MessageKind.MIRRORS_LIBRARY_NEW_EMITTER);
+        } else {
+          reportWarning(NO_LOCATION_SPANNABLE,
+             MessageKind.IMPORT_EXPERIMENTAL_MIRRORS,
+              {'importChain': importChains.join(
+                   MessageKind.IMPORT_EXPERIMENTAL_MIRRORS_PADDING)});
+        }
       }
 
       functionClass.ensureResolved(this);
       functionApplyMethod = functionClass.lookupLocalMember('apply');
 
       proxyConstant =
           resolver.constantCompiler.compileConstant(
               coreLibrary.find('proxy')).value;
 
       if (preserveComments) {
@@ skipping 1069 matching lines @@
     return futureClass.computeType(compiler).createInstantiation([elementType]);
   }
 
   @override
   InterfaceType streamType([DartType elementType = const DynamicType()]) {
     return streamClass.computeType(compiler).createInstantiation([elementType]);
   }
 }
 
 typedef void InternalErrorFunction(Spannable location, String message);