dart2js cps: Reanalyze subterms when they get inserted.

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

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
index fec259bd8d6cc501737f8f5ce6fefcaaf8b95b23..7d8edfa8bc458d047de7db23feb467c6d972a25f 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
@@ -223,9 +223,10 @@ class LetMutable extends Expression implements InteriorNode {
   accept(Visitor visitor) => visitor.visitLetMutable(this);
 }
 
-abstract class Invoke {
+abstract class Invoke implements Expression {
   Selector get selector;
   List<Reference<Primitive>> get arguments;
+  Reference<Continuation> get continuation;
 }
 
 /// Represents a node with a child node, which can be accessed through the