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

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

Index: pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
diff --git a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
index 9988f4724ea68fd59e8ee7567ff93ff64d214ae3..be5cc9c3a0df3efb84b023b8706cc9d0e887033c 100644
--- a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
+++ b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
@@ -246,8 +246,11 @@ class ShrinkingReducer extends Pass {
   }
 }
 
-/// 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) {