Complain if there are pending classes.

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 419 matching lines @@
   /// Map containing information about the warnings and hints that have been
   /// suppressed for each library.
   Map<Uri, SuppressionInfo> suppressedWarnings = <Uri, SuppressionInfo>{};
 
   final bool suppressWarnings;
 
   final api.CompilerOutputProvider outputProvider;
 
   bool disableInlining = false;
 
+  /// True if compilation was aborted with a [CompilerCancelledException]. Only
+  /// set after Future retuned by [run] has completed.
+  bool compilerWasCancelled = false;
+
   List<Uri> librariesToAnalyzeWhenRun;
 
   Tracer tracer;
 
   CompilerTask measuredTask;
   Element _currentElement;
   LibraryElement coreLibrary;
   LibraryElement isolateLibrary;
   LibraryElement isolateHelperLibrary;
   LibraryElement jsHelperLibrary;
@@ skipping 343 matching lines @@
     reportDiagnostic(null,
         MessageKind.GENERIC.message({'text': '$message'}),
         api.Diagnostic.VERBOSE_INFO);
   }
 
   Future<bool> run(Uri uri) {
     totalCompileTime.start();
 
     return new Future.sync(() => runCompiler(uri)).catchError((error) {
       if (error is CompilerCancelledException) {
+        compilerWasCancelled = true;
         log('Error: $error');
         return false;
       }
 
       try {
         if (!hasCrashed) {
           hasCrashed = true;
           if (error is SpannableAssertionFailure) {
             reportAssertionFailure(error);
           } else {
@@ skipping 988 matching lines @@
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }
 
 /// Information about suppressed warnings and hints for a given library.
 class SuppressionInfo {
   int warnings = 0;
   int hints = 0;
 }