Fixes for SingleContextManager after experiments with two big codebases.

pkg/analyzer/lib/plugin/resolver_provider.dart

Index: pkg/analyzer/lib/plugin/resolver_provider.dart
diff --git a/pkg/analyzer/lib/plugin/resolver_provider.dart b/pkg/analyzer/lib/plugin/resolver_provider.dart
index ed0e3667e96525ee66013f986887396bd9cc56cb..33bb3666534e9299a46202edd6b5a0dc2652eadc 100644
--- a/pkg/analyzer/lib/plugin/resolver_provider.dart
+++ b/pkg/analyzer/lib/plugin/resolver_provider.dart
@@ -11,8 +11,5 @@ import 'package:analyzer/src/generated/source.dart';
  * A function that will return a [UriResolver] that can be used to resolve a
  * specific kind of URI within the analysis context rooted at the given
  * [folder].
- *
- * The given [folder] may be `null` if analysis is performed in an environment
- * where URI resolution is always the same in any folder.
  */
 typedef UriResolver ResolverProvider(Folder folder);