Add Class/MemberDefinition to handle synthesized classes/members

tests/compiler/dart2js/closure/closure_test.dart

Index: tests/compiler/dart2js/closure/closure_test.dart
diff --git a/tests/compiler/dart2js/closure/closure_test.dart b/tests/compiler/dart2js/closure/closure_test.dart
index 4cac483d56a14b03c818a2aedda44397dc385ba2..c17877c9be54e19e44aa596f900e5642054b0cee 100644
--- a/tests/compiler/dart2js/closure/closure_test.dart
+++ b/tests/compiler/dart2js/closure/closure_test.dart
@@ -54,9 +54,12 @@ void computeKernelClosureData(Compiler compiler, MemberEntity member,
   KernelToElementMapForBuilding elementMap = backendStrategy.elementMap;
   GlobalLocalsMap localsMap = backendStrategy.globalLocalsMapForTesting;
   ClosureDataLookup closureDataLookup = backendStrategy.closureDataLookup;
+  MemberDefinition definition = elementMap.getMemberDefinition(member);
+  assert(definition.kind == MemberKind.regular,
+      failedAt(member, "Unexpected member definition $definition"));
   new ClosureIrChecker(actualMap, sourceSpanMap, elementMap, member,
           localsMap.getLocalsMap(member), closureDataLookup)
-      .run(elementMap.getMemberNode(member));
+      .run(definition.node);
 }
 
 /// Ast visitor for computing closure data.