ozone: Introduce ClientPixmap and ClientPixmapFactory for non-GPU processes.

ui/ozone/common/stub_native_pixmap_manager.h

+// Copyright 2015 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.
+
+#ifndef UI_OZONE_COMMON_STUB_NATIVE_PIXMAP_MANAGER_H_
+#define UI_OZONE_COMMON_STUB_NATIVE_PIXMAP_MANAGER_H_
+
+#include "ui/ozone/public/native_pixmap_manager.h"
+
+namespace ui {
+
+// Platforms which don't need to share native pixmap use this.
+// The caller takes ownership of the instance.
+NativePixmapManager* CreateStubNativePixmapManager();
+
+}  // namespace ui
+
+#endif  // UI_OZONE_COMMON_STUB_NATIVE_PIXMAP_MANAGER_H_