Fix crash on factory redirection to an unresolved class.

dart/sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: dart/sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/dart/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index f9bd17618db11285c38675d1db8eea22216f4293..3c8eebcc45640e4a9192a400b7eb07b3b0d032b6 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -2033,6 +2033,9 @@ class ResolverVisitor extends CommonResolverVisitor<Element> {
         !redirectionTarget.modifiers.isConst()) {
       error(node, MessageKind.CONSTRUCTOR_IS_NOT_CONST);
     }
+    constructor.defaultImplementation = redirectionTarget;
+    if (Elements.isUnresolved(redirectionTarget)) return;
+
     // TODO(ahe): Check that this doesn't lead to a cycle.  For now,
     // just make sure that the redirection target isn't itself a
     // redirecting factory.