Revert "dart2js cps: Refactor and optimize string concatenations."

pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
index 47fedb7793795eb69812f94102a19b4c142375dc..90c0b69577ac486b89976498474657cb73a978eb 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
@@ -385,6 +385,11 @@ class SubexpressionVisitor extends ExpressionVisitor<String> {
     return "$keyword $callName($args)";
   }
 
+  String visitConcatenateStrings(ConcatenateStrings node) {
+    String args = node.arguments.map(visitExpression).join(', ');
+    return "concat [$args]";
+  }
+
   String visitLiteralList(LiteralList node) {
     String values = node.values.map(visitExpression).join(', ');
     return "list [$values]";