Tests for exceptional situations in MemoryResourceProvider.

pkg/analysis_server/lib/src/resource.dart

Index: pkg/analysis_server/lib/src/resource.dart
diff --git a/pkg/analysis_server/lib/src/resource.dart b/pkg/analysis_server/lib/src/resource.dart
index af2280932388b2af55d9e0545f3fad6fe6a773d5..ba7f288b82b4c699fd723f6f63ee4e1fdf89eaf9 100644
--- a/pkg/analysis_server/lib/src/resource.dart
+++ b/pkg/analysis_server/lib/src/resource.dart
@@ -247,9 +247,6 @@ class MemoryResourceProvider implements ResourceProvider {
 
   Folder newFolder(String path) {
     path = posix.normalize(path);
-    if (path.isEmpty) {
-      throw new ArgumentError('Empty paths are not supported');
-    }
     if (!path.startsWith('/')) {
       throw new ArgumentError("Path must start with '/'");
     }