Use closure tracer to identify closures that are not passed to Function.apply

sdk/lib/_internal/compiler/implementation/inferrer/map_tracer.dart

Index: sdk/lib/_internal/compiler/implementation/inferrer/map_tracer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/inferrer/map_tracer.dart b/sdk/lib/_internal/compiler/implementation/inferrer/map_tracer.dart
index 76cc9e5ef336a0e8a08db490ef057d8044ddc165..0e98efa83c4e08d23b41538da21c568a04f3770f 100644
--- a/sdk/lib/_internal/compiler/implementation/inferrer/map_tracer.dart
+++ b/sdk/lib/_internal/compiler/implementation/inferrer/map_tracer.dart
@@ -25,7 +25,7 @@ Set<String> okMapSelectorsSet = new Set.from(
       "forEach",
       "remove"]);
 
-class MapTracerVisitor extends TracerVisitor {
+class MapTracerVisitor extends TracerVisitor<MapTypeInformation> {
   // These lists are used to keep track of newly discovered assignments to
   // the map. Note that elements at corresponding indices are expected to
   // belong to the same assignment operation.