MemoryResourceProvider.getFolder() should not create the folder.

pkg/analyzer/test/source/package_map_provider_test.dart

Index: pkg/analyzer/test/source/package_map_provider_test.dart
diff --git a/pkg/analyzer/test/source/package_map_provider_test.dart b/pkg/analyzer/test/source/package_map_provider_test.dart
index 1f6c956036cab557dabd5e162f3b2e57528ff7ed..5959e4249142902e195c692d2a6555ac40f4a160 100644
--- a/pkg/analyzer/test/source/package_map_provider_test.dart
+++ b/pkg/analyzer/test/source/package_map_provider_test.dart
@@ -33,8 +33,9 @@ class PubPackageMapProviderTest {
 
   void setUp() {
     resourceProvider = new MemoryResourceProvider();
-    sdk = new FolderBasedDartSdk(resourceProvider,
-        FolderBasedDartSdk.defaultSdkDirectory(resourceProvider));
+    Folder sdkFolder = resourceProvider
+        .newFolder(resourceProvider.convertPath('/Users/user/dart-sdk'));
+    sdk = new FolderBasedDartSdk(resourceProvider, sdkFolder);
     packageMapProvider = new PubPackageMapProvider(resourceProvider, sdk);
     projectPath = resourceProvider.convertPath('/path/to/project');
     projectFolder = resourceProvider.newFolder(projectPath);