Add transformLibraries for closure conversion

pkg/kernel/lib/transformations/closure/mock.dart

 // Copyright (c) 2016, 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 kernel.transformations.closure.mock;
 
 import '../../ast.dart'
     show
         Arguments,
         Block,
@@ skipping 50 matching lines @@
 ///       }
 ///       Context copy() {
 ///         Context c = new Context(list.length);
 ///         c.parent = parent;
 ///         c.list.setRange(0, list.length, list);
 ///         return c;
 ///       }
 ///     }
 ///
 /// Returns the mock.
-Class mockUpContext(CoreTypes coreTypes, Program program) {
+Library mockUpContextLibrary(CoreTypes coreTypes) {
   String fileUri = "dart:mock";
 
   ///     final List list;
   Field listField = new Field(new Name("list"),
       type: coreTypes.listClass.rawType, isFinal: true, fileUri: fileUri);
   Accessor listFieldAccessor = new ThisPropertyAccessor(
       listField.name, listField, null, TreeNode.noOffset);
 
   ///     var parent;
   Field parentField = new Field(new Name("parent"), fileUri: fileUri);
@@ skipping 113 matching lines @@
   Class contextClass = new Class(
       name: "Context",
       supertype: new Supertype(coreTypes.objectClass, const <DartType>[]),
       constructors: [constructor],
       fields: fields,
       procedures: procedures,
       fileUri: fileUri);
   Library mock =
       new Library(Uri.parse(fileUri), name: "mock", classes: [contextClass])
         ..fileUri = fileUri;
+
+  return mock;
+}
+
+Class mockUpContextForLibraries(CoreTypes coreTypes, List<Library> libraries) {
+  Library mock = mockUpContextLibrary(coreTypes);
+  Program parent = libraries.length > 0 ? libraries[0]?.parent : null;
+  libraries.add(mock);
+  mock.parent = parent;
+  parent?.uriToSource[mock.fileUri] = new Source(<int>[0], const <int>[]);
+  return mock.classes[0];
+}
+
+Class mockUpContextForProgram(CoreTypes coreTypes, Program program) {
+  Library mock = mockUpContextLibrary(coreTypes);
   program.libraries.add(mock);
   mock.parent = program;
   program.uriToSource[mock.fileUri] = new Source(<int>[0], const <int>[]);
-  return contextClass;
+  return mock.classes[0];
 }