cps-ir: Implement string concatenation.

pkg/compiler/lib/src/js/builder.dart

 // Copyright (c) 2013, 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.
 
 // Utilities for building JS ASTs at runtime.  Contains a builder class
 // and a parser that parses part of the language.
 
 part of js;
 
 
@@ skipping 331 matching lines @@
                       List<Expression> arguments) {
     return new Call(new PropertyAccess.field(receiver, fieldName), arguments);
   }
 }
 
 LiteralString string(String value) => js.string(value);
 LiteralNumber number(num value) => js.number(value);
 ArrayInitializer numArray(Iterable<int> list) => js.numArray(list);
 ArrayInitializer stringArray(Iterable<String> list) => js.stringArray(list);
 Call propertyCall(Expression receiver,
-                    String fieldName,
-                    List<Expression> arguments) {
+                  String fieldName,
+                  List<Expression> arguments) {
   return js.propertyCall(receiver, fieldName, arguments);
 }
 
 class MiniJsParserError {
   MiniJsParserError(this.parser, this.message) { }
 
   final MiniJsParser parser;
   final String message;
 
   String toString() {
@@ skipping 951 matching lines @@
   Catch parseCatch() {
     expectCategory(LPAREN);
     String identifier = lastToken;
     expectCategory(ALPHA);
     expectCategory(RPAREN);
     expectCategory(LBRACE);
     Block body = parseBlock();
     return new Catch(new VariableDeclaration(identifier), body);
   }
 }