JS: Format if statements with no else on a single line

lib/src/codegen/js_printer.dart

 // Copyright (c) 2015, 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.
 
 library dev_compiler.src.codegen.js_printer;
 
 import 'dart:convert' show JSON, JsonEncoder;
 import 'dart:io' show Directory, File, Platform, Process;
 
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 16 matching lines @@
   JS.JavaScriptPrintingContext context;
   if (emitSourceMaps) {
     var printer = new srcmaps.Printer(outFilename);
     context = new SourceMapPrintingContext(printer, outDir);
   } else {
     context = new JS.SimpleJavaScriptPrintingContext();
   }
 
   var opts = new JS.JavaScriptPrintingOptions(
       allowKeywordsInProperties: true,
+      allowSingleLineIfStatements: true,
       arrowFnBindThisWorkaround: arrowFnBindThisWorkaround);
   var jsNamer = new TemporaryNamer(jsTree);
   jsTree.accept(new JS.Printer(opts, context, localNamer: jsNamer));
 
   String text;
   if (context is SourceMapPrintingContext) {
     var printer = context.printer;
     printer.add('//# sourceMappingURL=$outFilename.map\n');
     // Write output file and source map
     text = printer.text;
@@ skipping 82 matching lines @@
       _currentTopLevelDeclaration == null;
       return;
     }
   }
 
   String _getIdentifier(AstNode node) {
     if (node is SimpleIdentifier) return node.name;
     return null;
   }
 }