Support constructor declarations in analyzer2dart.

pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart

Index: pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
diff --git a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
index e16192237cd66a55d055e4d620fdbef12e2bbb4d..e9b99b005687dbe15d8c3e925adbb18c1905942a 100644
--- a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
+++ b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
@@ -480,9 +480,9 @@ class ParentVisitor extends RecursiveVisitor {
   processConstructorDefinition(ConstructorDefinition node) {
     node.body.parent = node;
     int index = 0;
-    node.parameters.forEach((Parameter parameter) {
+    node.parameters.forEach((Definition parameter) {
       parameter.parent = node;
-      parameter.parent_index = index++;
+      if (parameter is Parameter) parameter.parent_index = index++;
     });
     node.initializers.forEach((Initializer i) => i.parent = node);
   }