Revert "dart2js cps: Maintain parent pointers instead of recomputing them."

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

Index: pkg/compiler/lib/src/cps_ir/redundant_phi.dart
diff --git a/pkg/compiler/lib/src/cps_ir/redundant_phi.dart b/pkg/compiler/lib/src/cps_ir/redundant_phi.dart
index 183f8e36ff2e6fe9815e65b94389b4d851a62ccc..693b612d6858c901c18fec4f69a8858e74027ad8 100644
--- a/pkg/compiler/lib/src/cps_ir/redundant_phi.dart
+++ b/pkg/compiler/lib/src/cps_ir/redundant_phi.dart
@@ -15,13 +15,16 @@ import 'optimizers.dart';
 /// (except for feedback). Redundant parameters are removed from the
 /// continuation signature, all invocations, and replaced within the
 /// continuation body.
-class RedundantPhiEliminator extends TrampolineRecursiveVisitor implements Pass {
+class RedundantPhiEliminator extends RecursiveVisitor implements Pass {
   String get passName => 'Redundant phi elimination';
 
   final Set<Continuation> workSet = new Set<Continuation>();
 
   @override
   void rewrite(FunctionDefinition root) {
+    // Set all parent pointers.
+    new ParentVisitor().visit(root);
+
     // Traverse the tree once to build the work set.
     visit(root);