Revert "Remove Compiler.assembledCode."

tests/compiler/dart2js/compiler_alt.dart

+// Copyright (c) 2014, 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.
+
+/// Alternative compile method for dart2js commandline that stores the compiler
+/// for later inspection.
+///
+/// Use this in testing to inspect the compiler after compilation by setting
+/// the `compileFunc` variable in `package:compiler/src/dart2js.dart`
+/// to [compiler] before calling the `internalMain` function.
+
+library dart2js.alt;
+
+import 'dart:async';
+import 'package:compiler/compiler.dart';
+import 'package:compiler/src/apiimpl.dart';
+
+Compiler compiler;
+
+Future<String> compile(Uri script,
+                       Uri libraryRoot,
+                       Uri packageRoot,
+                       CompilerInputProvider inputProvider,
+                       DiagnosticHandler handler,
+                       [List<String> options = const [],
+                        CompilerOutputProvider outputProvider,
+                        Map<String, dynamic> environment = const {}]) {
+  if (!libraryRoot.path.endsWith("/")) {
+    throw new ArgumentError("libraryRoot must end with a /");
+  }
+  if (packageRoot != null && !packageRoot.path.endsWith("/")) {
+    throw new ArgumentError("packageRoot must end with a /");
+  }
+  compiler = new Compiler(inputProvider,
+                          outputProvider,
+                          handler,
+                          libraryRoot,
+                          packageRoot,
+                          options,
+                          environment);
+  return compiler.run(script).then((_) {
+    String code = compiler.assembledCode;
+    if (code != null && outputProvider != null) {
+      code = ''; // Non-null signals success.
+    }
+    return code;
+  });
+}