Revert "Revert "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 7f3458d79edb90b1dee5239f95575844aa711c3f..bda22d2add56cd5027966f9c57c3be6301433cd1 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];