Change Maps to HashMaps to save in performance, index and generated directories not touched

pkg/analysis_server/lib/src/package_uri_resolver.dart

Index: pkg/analysis_server/lib/src/package_uri_resolver.dart
diff --git a/pkg/analysis_server/lib/src/package_uri_resolver.dart b/pkg/analysis_server/lib/src/package_uri_resolver.dart
index 2aaaca94a8b6415711177fe0307d244578314784..6de45078b65b9f4c9202b2f26b1ed6b2b962a404 100644
--- a/pkg/analysis_server/lib/src/package_uri_resolver.dart
+++ b/pkg/analysis_server/lib/src/package_uri_resolver.dart
@@ -4,6 +4,8 @@
 
 library resolver.package;
 
+import 'dart:collection';
+
 import 'package:analysis_server/src/resource.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 
@@ -22,7 +24,7 @@ class PackageMapUriResolver extends UriResolver {
    * A table mapping package names to the path of the directories containing
    * the package.
    */
-  final Map<String, List<Folder>> packageMap;
+  final HashMap<String, List<Folder>> packageMap;
 
   /**
    * The [ResourceProvider] for this resolver.