Remove _LibraryNode altogether.

pkg/analyzer/lib/src/dart/analysis/file_state.dart

Index: pkg/analyzer/lib/src/dart/analysis/file_state.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/file_state.dart b/pkg/analyzer/lib/src/dart/analysis/file_state.dart
index 3540d69d60ce61cf26815874452b81fa19e91cd7..3a88ed6aafa1ed2f4ca9d76944a18d5ac2b49d9c 100644
--- a/pkg/analyzer/lib/src/dart/analysis/file_state.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/file_state.dart
@@ -209,6 +209,11 @@ class FileState {
    */
   UnlinkedUnit get unlinked => _unlinked;
 
+  /**
+   * Return the [uri] string.
+   */
+  String get uriStr => uri.toString();
+
   @override
   bool operator ==(Object other) {
     return other is FileState && other.uri == uri;