Fix some bugs regarding native fields.

dart/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 662 matching lines @@
           pleaseReportCrash();
         }
       } catch (doubleFault) {
         // Ignoring exceptions in exception handling.
       }
       rethrow;
     } finally {
       tracer.close();
       totalCompileTime.stop();
     }
-    return true;
+    return !compilationFailed;
   }
 
   bool hasIsolateSupport() => isolateLibrary != null;
 
   /**
    * This method is called before [library] import and export scopes have been
    * set up.
    */
   void onLibraryScanned(LibraryElement library, Uri uri) {
     if (dynamicClass != null) {
@@ skipping 254 matching lines @@
       libraries.forEach((_, lib) => fullyEnqueueLibrary(lib, enqueuer.codegen));
     }
     processQueue(enqueuer.codegen, main);
     enqueuer.codegen.logSummary(log);
 
     if (compilationFailed) return;
 
     backend.assembleProgram();
 
     checkQueues();
+
+    if (compilationFailed) {
+      assembledCode = null; // Signals failure.
+    }
   }
 
   void fullyEnqueueLibrary(LibraryElement library, Enqueuer world) {
     void enqueueAll(Element element) {
       fullyEnqueueTopLevelElement(element, world);
     }
     library.implementation.forEachLocalMember(enqueueAll);
   }
 
   void fullyEnqueueTopLevelElement(Element element, Enqueuer world) {
@@ skipping 481 matching lines @@
 
   void close() {}
 
   toString() => name;
 
   /// Convenience method for getting an [api.CompilerOutputProvider].
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }