Remove unused method and field from DartSdkManager

pkg/analyzer/test/stress/for_git_repository.dart

Index: pkg/analyzer/test/stress/for_git_repository.dart
diff --git a/pkg/analyzer/test/stress/for_git_repository.dart b/pkg/analyzer/test/stress/for_git_repository.dart
index 445dd4b9a0c051fe67b74febddb96e6dbc04f83d..0fe14f3d9a9cec7cbead38c6bd55835769df9115 100644
--- a/pkg/analyzer/test/stress/for_git_repository.dart
+++ b/pkg/analyzer/test/stress/for_git_repository.dart
@@ -244,8 +244,7 @@ class StressTest {
     pathContext = resourceProvider.pathContext;
     fs.Folder sdkDirectory =
         FolderBasedDartSdk.defaultSdkDirectory(resourceProvider);
-    sdkManager = new DartSdkManager(sdkDirectory.path, false,
-        (_) => new FolderBasedDartSdk(resourceProvider, sdkDirectory));
+    sdkManager = new DartSdkManager(sdkDirectory.path, false);
     contentCache = new ContentCache();
     ContextBuilder builder =
         new ContextBuilder(resourceProvider, sdkManager, contentCache);