ui + mus: Split ContextFactory into ContextFactory(Client) and ContextFactoryPrivate

ui/compositor/test/context_factories_for_test.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 namespace ui {
 
 class ContextFactory;
+class ContextFactoryPrivate;
 
 // Set up the compositor ContextFactory for a test environment. Unit tests
 // that do not have a full content environment need to call this before
 // initializing the Compositor.
 // Some tests expect pixel output, and they should pass true for
 // |enable_pixel_output|. Most unit tests should pass false. Once this has been
 // called, the caller must call TerminateContextFactoryForTests() to clean up.
 // TODO(sky): this should return a scoped_ptr and then nuke
 // TerminateContextFactoryForTests().
-ui::ContextFactory* InitializeContextFactoryForTests(bool enable_pixel_output);
+void InitializeContextFactoryForTests(
+    bool enable_pixel_output,
+    ui::ContextFactory** context_factory,
+    ui::ContextFactoryPrivate** context_factory_private);
+
 void TerminateContextFactoryForTests();
 
 }  // namespace ui