dart2js cps: Refactor and optimize string concatenations.

pkg/compiler/lib/src/constants/expressions.dart

Index: pkg/compiler/lib/src/constants/expressions.dart
diff --git a/pkg/compiler/lib/src/constants/expressions.dart b/pkg/compiler/lib/src/constants/expressions.dart
index 1bcf8e3ba5578253b586ca02bb9fc8a348b2b5ee..5644b0f5847ce5db238ce8f803a226a1c2904470 100644
--- a/pkg/compiler/lib/src/constants/expressions.dart
+++ b/pkg/compiler/lib/src/constants/expressions.dart
@@ -1531,15 +1531,6 @@ abstract class ConstantExpressionVisitor<R, A> {
   R visitNamed(NamedArgumentReference exp, A context);
 }
 
-/// Represents the declaration of a constant [element] with value [expression].
-// TODO(johnniwinther): Where does this class belong?
-class ConstDeclaration {
-  final VariableElement element;
-  final ConstantExpression expression;
-
-  ConstDeclaration(this.element, this.expression);
-}
-
 class ConstExpPrinter extends ConstantExpressionVisitor {
   final StringBuffer sb = new StringBuffer();