Redo "Steps towards making dart2js JS AST templates an indepentent library."

tests/compiler/dart2js/async_await_js_transform_test.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.
 
 import "package:expect/expect.dart";
 import "package:compiler/src/js/js.dart";
 import "package:compiler/src/js/rewrite_async.dart";
 
 import "backend_dart/dart_printer_test.dart" show PrintDiagnosticListener;
 
 void testTransform(String source, String expected) {
   Fun fun = js(source);
   Fun rewritten = new AsyncRewriter(
       null, // The diagnostic helper should not be used in these tests.
       null,
       thenHelper: new VariableUse("thenHelper"),
       newCompleter: new VariableUse("Completer"),
       endOfIteration: new VariableUse("endOfIteration"),
       newIterable: new VariableUse("Iterator"),
       safeVariableName: (String name) => "__$name").rewrite(fun);
-  Printer printer = new Printer(new PrintDiagnosticListener(), null);
+ 
+  JavaScriptPrintingOptions options = new JavaScriptPrintingOptions();
+  JavaScriptPrintingContext context = new SimpleJavaScriptPrintingContext();
+  Printer printer = new Printer(options, context);
   printer.visit(rewritten);
-  Expect.stringEquals(expected, printer.outBuffer.getText());
+  Expect.stringEquals(expected, context.getText());
 }
 
 main() {
   testTransform("""
 function() async {
   print(this.x); // Ensure `this` is translated in the helper function.
   await foo();
 }""", """
 function() {
   var __goto = 0, __completer = new Completer(), __self = this;
@@ skipping 902 matching lines @@
           break;
         case 3:
           // after while
         case 1:
           // return
           return thenHelper(__returnValue, null, __completer, null);
       }
   }
   return thenHelper(null, __helper, __completer, null);
 }""");
-}
+}