Create new interface instead of ClosureClassMap for variable usage information that is not Element-…

pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart

Index: pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
index 94fb3f53d68140e28b9819b04f20caee0b7e7bae..013c301a2741b9ada7b642e4df20d988dec36b83 100644
--- a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
@@ -124,7 +124,7 @@ class KernelAstAdapter extends KernelToElementMapMixin
       // Closures require a lookup one level deeper in the closure class mapper.
       if (target == null) {
         MethodElement originTargetFunction = originTarget;
-        ClosureClassMap classMap = _compiler.closureToClassMapper
+        ClosureRepresentationInfo classMap = _compiler.closureToClassMapper
             .getClosureToClassMapping(originTargetFunction);
         if (classMap.closureElement != null) {
           target = kernel.localFunctions[classMap.closureElement];