dart2js cps: Refactor CallExpressions into Primitives.

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

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.cps_ir.mutable_ssa;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
 
 /// Determines which mutable variables should be rewritten to phi assignments
@@ skipping 150 matching lines @@
           mergeHints(variable, setter.value.definition);
           setter.value.unlink();
           node.remove();
         }
       } else if (node is LetPrim && node.primitive is GetMutable) {
         GetMutable getter = node.primitive;
         MutableVariable variable = getter.variable.definition;
         if (shouldRewrite(variable)) {
           // Replace with the reaching definition from the environment.
           Primitive value = environment[variable];
-          value.substituteFor(getter);
+          getter.replaceUsesWith(value);
           mergeHints(variable, value);
           node.remove();
         }
       } else if (node is LetCont) {
         // Create phi parameters for each join continuation bound here, and put
         // them on the stack for later processing.
         // Note that non-join continuations are handled at the use-site.
         for (Continuation cont in node.continuations) {
           if (!isJoinContinuation(cont)) continue;
           // Create a phi parameter for every mutable variable in scope.
@@ skipping 60 matching lines @@
 class VariableItem extends StackItem {}
 
 /// Represents a yet unprocessed continuation together with the
 /// environment in which to process it.
 class ContinuationItem extends StackItem {
   final Continuation continuation;
   final Map<MutableVariable, Primitive> environment;
 
   ContinuationItem(this.continuation, this.environment);
 }