Get rid of library proto information for debugger libraries

tool/input_sdk/private/debugger.dart

Index: tool/input_sdk/private/debugger.dart
diff --git a/tool/input_sdk/private/debugger.dart b/tool/input_sdk/private/debugger.dart
index cbdea128503e9f97359f1beac4e7812208c68f0e..a6bc9639f2b7b9205f002c83db3fce2bd4828552 100644
--- a/tool/input_sdk/private/debugger.dart
+++ b/tool/input_sdk/private/debugger.dart
@@ -507,17 +507,12 @@ class ObjectFormatter extends Formatter {
 
 /// Formatter for module Dart Library objects.
 class LibraryModuleFormatter implements Formatter {
-  String libraryName;
-
-  accept(object, config) {
-    libraryName = dart.getDartLibraryName(object);
-    return libraryName != null;
-  }
+  accept(object, config) => dart.getDartLibraryName(object) != null;
 
   bool hasChildren(object) => true;
 
   String preview(object) {
-    var libraryNames = libraryName.split('/');
+    var libraryNames = dart.getDartLibraryName(object).split('/');
     // Library names are received with a repeat directory name, so strip the
     // last directory entry here to make the path cleaner. For example, the
     // library "third_party/dart/utf/utf" shoud display as