dart2js cps: Streamline expressions and primitives.

pkg/compiler/lib/src/cps_ir/cps_fragment.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 cps_ir.cps_fragment;
 
 import 'cps_ir_nodes.dart';
 import '../constants/values.dart';
 import '../universe/universe.dart' show Selector;
 import '../types/types.dart' show TypeMask;
@@ skipping 260 matching lines @@
     other.root = null;
   }
 
   /// Reads the value of the given mutable variable.
   Primitive getMutable(MutableVariable variable) {
     return letPrim(new GetMutableVariable(variable));
   }
 
   /// Sets the value of the given mutable variable.
   void setMutable(MutableVariable variable, Primitive value) {
-    SetMutableVariable setter = new SetMutableVariable(variable, value);
-    put(setter);
-    context = setter;
+    letPrim(new SetMutableVariable(variable, value));
   }
 
   /// Declare a new mutable variable.
   void letMutable(MutableVariable variable, Primitive initialValue) {
     LetMutable let = new LetMutable(variable, initialValue);
     put(let);
     context = let;
   }
 }