Enable user change background image in settings page in Aura build.

ash/desktop_background/desktop_background_resources.h

Index: ash/desktop_background/desktop_background_resources.h
diff --git a/ash/desktop_background/desktop_background_resources.h b/ash/desktop_background/desktop_background_resources.h
new file mode 100644
index 0000000000000000000000000000000000000000..06b0dd9ec67bc91c3425793e902f7c7a4fb37188
--- /dev/null
+++ b/ash/desktop_background/desktop_background_resources.h
@@ -0,0 +1,25 @@
+// Copyright (c) 2012 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 ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_RESOURCES_H_
+#define ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_RESOURCES_H_
+
+class SkBitmap;
+
+namespace ash {
+
+// This probably needs to put to another place. But I am not sure where is the
+// best place. It's basically util function which used both by ash and by
+// webui handler.

[flackr, 2012/03/07 20:50:28]

Remove comment or change to TODO. Given that you have accessors for the
WallPaper, WallpaperThumbnail, you could probably add one for WallpaperCount and
remove these from being global variables.

[bshe, 2012/03/07 23:48:35]

Put them behind internal namespace. Not sure if that's what you mean though...

[flackr, 2012/03/08 01:19:58]

Nope. What I meant was that the functions give you all of these constants so
they can be removed from the header file and only defined in the .cc file in an
anonymous namespace (see comment in .cc file).

[bshe, 2012/03/08 03:19:24]

Done.

+extern const int kDefaultWallpaperResources[];
+extern const int kDefaultWallpaperResourcesThumb[];
+extern const int kDefaultWallpaperCount;
+extern const int kPresetWallpaperIndex;
+
+const SkBitmap& GetDefaultWallpaper(int index);
+const SkBitmap& GetDefaultWallpaperThumbnail(int index);
+
+}  // namespace ash
+
+#endif  // ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_RESOURCES_H_