Create map for dump_info on demand.

pkg/compiler/lib/src/resolution/tree_elements.dart

Index: pkg/compiler/lib/src/resolution/tree_elements.dart
diff --git a/pkg/compiler/lib/src/resolution/tree_elements.dart b/pkg/compiler/lib/src/resolution/tree_elements.dart
index a60bb79b469c79eb5a38363f8ff6173252075c6b..869ea6b3245b5027ab5b9699408700641e348fa7 100644
--- a/pkg/compiler/lib/src/resolution/tree_elements.dart
+++ b/pkg/compiler/lib/src/resolution/tree_elements.dart
@@ -111,7 +111,11 @@ class TreeElementMapping extends TreeElements {
   Map<Spannable, Selector> _selectors;
   Map<Spannable, TypeMask> _typeMasks;
   Map<Node, DartType> _types;
-  Map<Node, DartType> typesCache = <Node, DartType>{};
+
+  Map<Node, DartType> _typesCache;
+  Map<Node, DartType> get typesCache =>
+      _typesCache ?? _typesCache = <Node, DartType>{};

[Siggi Cherem (dart-lang), 2016/03/09 19:15:03]

replace with `_typesCache ??= <Node, DartType>{}`?

+
   Setlet<SourceSpan> _superUses;
   Map<Node, ConstantExpression> _constants;
   Map<VariableElement, List<Node>> _potentiallyMutated;