Turn a Dart String + String into a JavaScript String + String.

sdk/lib/_internal/compiler/implementation/ssa/codegen.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 1488 matching lines @@
       if (target == backend.jsArrayAdd) {
         methodName = 'push';
       } else if (target == backend.jsArrayRemoveLast) {
         methodName = 'pop';
       } else if (target == backend.jsStringSplit) {
         methodName = 'split';
         // Split returns a List, so we make sure the backend knows the
         // list class is instantiated.
         world.registerInstantiatedClass(
             compiler.listClass, work.resolutionTree);
-      } else if (target == backend.jsStringConcat) {
+      } else if (target == backend.jsStringOperatorAdd) {
         push(new js.Binary('+', object, arguments[0]), node);
         return;
       } else if (target.isNative() && target.isFunction()
                  && !node.isInterceptedCall) {
         // A direct (i.e. non-interceptor) native call is the result of
         // optimization.  The optimization ensures any type checks or
         // conversions have been satisified.
         methodName = target.fixedBackendName();
       }
     }
@@ skipping 1471 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive(compiler) && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }