Work around naming conflict in analyzer's Resource class.

pkg/analyzer/lib/file_system/physical_file_system.dart

Index: pkg/analyzer/lib/file_system/physical_file_system.dart
diff --git a/pkg/analyzer/lib/file_system/physical_file_system.dart b/pkg/analyzer/lib/file_system/physical_file_system.dart
index 9c9d5a607b326561ace6f983bc9130b4d79641d6..d9497df78ae7cdbbc3da69bd8202cdd4ddca8af9 100644
--- a/pkg/analyzer/lib/file_system/physical_file_system.dart
+++ b/pkg/analyzer/lib/file_system/physical_file_system.dart
@@ -5,6 +5,7 @@
 library physical_file_system;
 
 import 'dart:async';
+import 'dart:core' hide Resource;
 import 'dart:io' as io;
 
 import 'package:analyzer/src/generated/java_io.dart';
@@ -73,7 +74,7 @@ class PhysicalResourceProvider implements ResourceProvider {
  */
 class _PhysicalFile extends _PhysicalResource implements File {
   _PhysicalFile(io.File file) : super(file);
- 
+
   @override
   Stream<WatchEvent> get changes => new FileWatcher(_entry.path).events;