Generative constructors in the new dart backend.

pkg/compiler/lib/src/tree_ir/optimization/optimization.dart

Index: pkg/compiler/lib/src/tree_ir/optimization/optimization.dart
diff --git a/pkg/compiler/lib/src/tree_ir/optimization/optimization.dart b/pkg/compiler/lib/src/tree_ir/optimization/optimization.dart
index 737ac3fdab68a7bbeb5be0ea25c292297a0a004c..ff815ba7caf4841dfa74e182f74f45f1c756e557 100644
--- a/pkg/compiler/lib/src/tree_ir/optimization/optimization.dart
+++ b/pkg/compiler/lib/src/tree_ir/optimization/optimization.dart
@@ -15,6 +15,7 @@ abstract class Pass {
   void rewrite(ExecutableDefinition root) => root.applyPass(this);
   void rewriteFieldDefinition(FieldDefinition root);
   void rewriteFunctionDefinition(FunctionDefinition root);
+  void rewriteConstructorDefinition(ConstructorDefinition root);
 }
 
 
@@ -29,4 +30,8 @@ abstract class PassMixin implements Pass {
     if (root.isAbstract) return;
     rewriteExecutableDefinition(root);
   }
+  void rewriteConstructorDefinition(ConstructorDefinition root) {
+    if (root.isAbstract) return;
+    rewriteExecutableDefinition(root);
+  }
 }