Reduce test.dart memory usage.

tools/testing/dart/compiler_configuration.dart

 // Copyright (c) 2014, 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 compiler_configuration;
 
 import 'dart:io' show
     Platform;
 
 import 'runtime_configuration.dart' show
@@ skipping 252 matching lines @@
   List<String> computeRuntimeArguments(
       RuntimeConfiguration runtimeConfiguration,
       String buildDir,
       TestInformation info,
       List<String> vmOptions,
       List<String> sharedOptions,
       List<String> originalArguments,
       CommandArtifact artifact) {
     Uri sdk = useSdk ?
         nativeDirectoryToUri(buildDir).resolve('dart-sdk/') :
-        nativeDirectoryToUri(TestUtils.dartDir().toNativePath())
-                                                .resolve('sdk/');
+        nativeDirectoryToUri(TestUtils.dartDir.toNativePath()).resolve('sdk/');
     Uri preambleDir = sdk.resolve('lib/_internal/lib/preambles/');
     return runtimeConfiguration.dart2jsPreambles(preambleDir)
         ..add(artifact.filename);
   }
 }
 
 /// Configuration for dart2dart compiler.
 class Dart2dartCompilerConfiguration extends Dart2xCompilerConfiguration {
   Dart2dartCompilerConfiguration({
       bool isDebug,
@@ skipping 98 matching lines @@
       bool isDebug,
       bool isChecked,
       bool isHostChecked,
       bool useSdk})
       : super(
           'dart2analyzer', isDebug: isDebug, isChecked: isChecked,
           isHostChecked: isHostChecked, useSdk: useSdk);
 
   String computeCompilerPath(String buildDir) => 'editor/tools/analyzer';
 }