Revert "dart2js cps: Add helpers for common IR manipulation."

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

Index: pkg/compiler/lib/src/cps_ir/mutable_ssa.dart
diff --git a/pkg/compiler/lib/src/cps_ir/mutable_ssa.dart b/pkg/compiler/lib/src/cps_ir/mutable_ssa.dart
index e2252c4d55eecf9c45e77f541b1c1db126ad722c..3dea17c0ba40cf1418c74a096b7e34dcecd095c0 100644
--- a/pkg/compiler/lib/src/cps_ir/mutable_ssa.dart
+++ b/pkg/compiler/lib/src/cps_ir/mutable_ssa.dart
@@ -114,6 +114,12 @@ class MutableVariableEliminator implements Pass {
            cont.firstRef.parent is InvokeContinuation;
   }
 
+  void removeNode(InteriorNode node) {
+    InteriorNode parent = node.parent;
+    parent.body = node.body;
+    node.body.parent = parent;
+  }
+
   /// If some useful source information is attached to exactly one of the
   /// two definitions, the information is copied onto the other.
   void mergeHints(MutableVariable variable, Primitive value) {
@@ -133,8 +139,7 @@ class MutableVariableEliminator implements Pass {
   /// Continuations to be processed are put on the stack for later processing.
   void processBlock(Expression node,
                     Map<MutableVariable, Primitive> environment) {
-    Expression next = node.next;
-    for (; node is! TailExpression; node = next, next = node.next) {
+    for (; node is! TailExpression; node = node.next) {
       if (node is LetMutable && shouldRewrite(node.variable)) {
         // Put the new mutable variable on the stack while processing the body,
         // and pop it off again when done with the body.
@@ -150,7 +155,7 @@ class MutableVariableEliminator implements Pass {
 
         // Remove the mutable variable binding.
         node.value.unlink();
-        node.remove();
+        removeNode(node);
       } else if (node is LetPrim && node.primitive is SetMutable) {
         SetMutable setter = node.primitive;
         MutableVariable variable = setter.variable.definition;
@@ -160,7 +165,7 @@ class MutableVariableEliminator implements Pass {
           environment[variable] = setter.value.definition;
           mergeHints(variable, setter.value.definition);
           setter.value.unlink();
-          node.remove();
+          removeNode(node);
         }
       } else if (node is LetPrim && node.primitive is GetMutable) {
         GetMutable getter = node.primitive;
@@ -170,7 +175,7 @@ class MutableVariableEliminator implements Pass {
           Primitive value = environment[variable];
           value.substituteFor(getter);
           mergeHints(variable, value);
-          node.remove();
+          removeNode(node);
         }
       } else if (node is LetCont) {
         // Create phi parameters for each join continuation bound here, and put