Make isEmpty a getter.

utils/tests/pub/version_solver_test.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.
 
 library pub_update_test;
 
 import 'dart:io';
 import 'dart:isolate';
 
 import '../../pub/lock_file.dart';
@@ skipping 386 matching lines @@
     // Resolve the versions.
     var future = resolveVersions(sources, root, realLockFile);
 
     if (result != null) {
       expect(future, completion(predicate((actualResult) {
         for (var actualId in actualResult) {
           if (!result.containsKey(actualId.name)) return false;
           var expectedId = result.remove(actualId.name);
           if (actualId != expectedId) return false;
         }
-        return result.isEmpty();
+        return result.isEmpty;
       }, description: 'packages to match $result')));
     } else if (error == noVersion) {
       expect(future, throwsA(new isInstanceOf<NoVersionException>()));
     } else if (error == disjointConstraint) {
       expect(future, throwsA(new isInstanceOf<DisjointConstraintException>()));
     } else if (error == sourceMismatch) {
       expect(future, throwsA(new isInstanceOf<SourceMismatchException>()));
     } else if (error == descriptionMismatch) {
       expect(future, throwsA(new isInstanceOf<DescriptionMismatchException>()));
     } else if (error == couldNotSolve) {
@@ skipping 106 matching lines @@
   var match = new RegExp(r"(.*) from (.*)").firstMatch(name);
   if (match == null) return new Pair<String, Source>(name, source1);
   switch (match[2]) {
   case 'mock1': return new Pair<String, Source>(match[1], source1);
   case 'mock2': return new Pair<String, Source>(match[1], source2);
   case 'root': return new Pair<String, Source>(match[1], rootSource);
   case 'versionless':
     return new Pair<String, Source>(match[1], versionlessSource);
   }
 }