dart2js cps: Replace getter/setter calls with direct field access.

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

 // Copyright (c) 2014, 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.shrinking_reductions;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
 
 /**
@@ skipping 228 matching lines @@
     }
     parameters.removeLast();
 
     // Removing an unused parameter can create an eta-redex.
     if (_isEtaCont(continuation)) {
       _worklist.add(new _ReductionTask(_ReductionKind.ETA_CONT, continuation));
     }
   }
 }
 
-/// Returns true iff the bound primitive is unused.
-bool _isDeadVal(LetPrim node) => !node.primitive.hasAtLeastOneUse;
+/// Returns true iff the bound primitive is unused, and has no effects
+/// preventing it from being eliminated.
+bool _isDeadVal(LetPrim node) {
+  return node.primitive.hasNoUses && node.primitive.isSafeForElimination;
+}
 
 /// Returns true iff the continuation is unused.
 bool _isDeadCont(Continuation cont) {
   return !cont.isReturnContinuation && !cont.hasAtLeastOneUse;
 }
 
 /// Returns true iff the continuation has a body (i.e., it is not the return
 /// continuation), it is used exactly once, and that use is as the continuation
 /// of a continuation invocation.
 bool _isBetaContLin(Continuation cont) {
@@ skipping 451 matching lines @@
   }
 
   String toString() => "$kind: $node";
 }
 
 /// A dummy class used solely to mark nodes as deleted once they are removed
 /// from a term.
 class _DeletedNode extends Node {
   accept(_) => null;
 }