Reduce use of getClosureInfoForMember and cleanup closure_test

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 c6e14f3103591995b0212630b497131d962ae64c..e964208eed16c3b70d996ef8ff99b931e8c4807d 100644
--- a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
@@ -133,13 +133,8 @@ class KernelAstAdapter extends KernelToElementMapBaseMixin
       target = kernel.functions[originTarget];
       // Closures require a lookup one level deeper in the closure class mapper.
       if (target == null) {
-        MethodElement originTargetFunction = originTarget;
-        ClosureRepresentationInfo classMap = _compiler
-            .backendStrategy.closureDataLookup
-            .getClosureInfoForMember(originTargetFunction);
-        if (classMap.closureEntity != null) {
-          target = kernel.localFunctions[classMap.closureEntity];
-        }
+        SynthesizedCallMethodElementX originTargetFunction = originTarget;
+        target = kernel.localFunctions[originTargetFunction.expression];
       }
     } else if (originTarget is FieldElement) {
       target = kernel.fields[originTarget];