Incremental compilation of new classes with fields.

dart/pkg/dart2js_incremental/lib/caching_compiler.dart

 // Copyright (c) 2013, 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_incremental;
 
 /// Do not call this method directly. It will be made private.
 // TODO(ahe): Make this method private.
 Future<Compiler> reuseCompiler(
     {DiagnosticHandler diagnosticHandler,
@@ skipping 38 matching lines @@
         print('Unable to reuse compiler due to cancel.');
       } else if (compiler.enqueuer.resolution.hasEnqueuedReflectiveElements) {
         print('Unable to reuse compiler due to dart:mirrors.');
       } else if (compiler.deferredLoadTask.isProgramSplit) {
         print('Unable to reuse compiler due to deferred loading.');
       } else {
         print('Unable to reuse compiler.');
       }
     }
     oldTag.makeCurrent();
-    return new Future.value(
-        new Compiler(
-            inputProvider,
-            outputProvider,
-            diagnosticHandler,
-            libraryRoot,
-            packageRoot,
-            options,
-            environment));
+    compiler = new Compiler(
+        inputProvider,
+        outputProvider,
+        diagnosticHandler,
+        libraryRoot,
+        packageRoot,
+        options,
+        environment);
+    JavaScriptBackend backend = compiler.backend;
+    // Much like a scout, an incremental compiler is always prepared. For
+    // mixins, at least.
+    backend.emitter.oldEmitter.needsMixinSupport = true;
+    return new Future.value(compiler);
   } else {
     for (final task in compiler.tasks) {
       if (task.watch != null) {
         task.watch.reset();
       }
     }
     compiler
         ..outputProvider = outputProvider
         ..provider = inputProvider
         ..handler = diagnosticHandler
@@ skipping 71 matching lines @@
             library.isPlatformLibrary ||
             (packagesAreImmutable && library.isPackageLibrary));
       };
     }
     return compiler.libraryLoader.resetAsync(reuseLibrary).then((_) {
       oldTag.makeCurrent();
       return compiler;
     });
   }
 }