dart2js cps: Fix a couple of minor issues.

pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart

Index: pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
diff --git a/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart b/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
index 68b84593ebdbc9b236477d96851e83fd25ef4a24..bad76909807a1877fde5eadd09770db1006a9cfb 100644
--- a/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
+++ b/pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart
@@ -307,7 +307,7 @@ class StatementRewriter extends Transformer implements Pass {
       // Handle constant assignments specially.
       // They are always safe to propagate (though we should avoid duplication).
       // Moreover, they should not prevent other expressions from propagating.
-      if (assign.variable.readCount <= 1) {
+      if (assign.variable.readCount == 1) {

[asgerf, 2015/06/29 14:09:12]

This matters when there is a dead variable due to optimizations being disabled.

         // A single-use constant should always be propagted to its use site.
         constantEnvironment[assign.variable] = assign.value;
         --assign.variable.writeCount;