Move all wallpaper file loading and decoding from DesktopBackgroundController to WallpaperManager.

ash/shell/content_client/shell_browser_main_parts.cc

Index: ash/shell/content_client/shell_browser_main_parts.cc
diff --git a/ash/shell/content_client/shell_browser_main_parts.cc b/ash/shell/content_client/shell_browser_main_parts.cc
index 7a745c6b833e3f92e756f3d833736edaacf4bde7..02017e62d673f71e97f191ce7ea75e31104e6b73 100644
--- a/ash/shell/content_client/shell_browser_main_parts.cc
+++ b/ash/shell/content_client/shell_browser_main_parts.cc
@@ -37,6 +37,7 @@
 #endif
 
 #if defined(OS_CHROMEOS)
+#include "chrome/browser/chromeos/login/wallpaper_manager.h"
 #include "chromeos/audio/cras_audio_handler.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #endif
@@ -134,8 +135,10 @@ void ShellBrowserMainParts::PreMainMessageLoopRun() {
 
   ash::shell::InitWindowTypeLauncher();
 
-  Shell::GetInstance()->desktop_background_controller()->SetDefaultWallpaper(

[Alexander Alekseev, 2014/04/09 14:37:38]

Scott, can I completely remove this call? (you've added it back in 2012).
DesktopBackgroundController will not have SetDefaultWallpaper() method, so to
set default wallpaper we would need to call UserWallpaperDelegate here.

It seems that wallpaper (now) will be set in Shell::Init() :
https://code.google.com/p/chromium/codesearch#chromium/src/ash/shell.cc&l=983

Can I completely remove SetDefaultWallpaper here?

-      false /* is_guest */);
+#if defined(OS_CHROMEOS)
+  chromeos::WallpaperManager::Get()->
+      SetDefaultWallpaperDelayed(chromeos::UserManager::kSignInUser);

[Alexander Alekseev, 2014/04/08 16:34:20]

This breaks dependencies.
Should I remove this call completely?
It would work for ChromeOS, but will it break some other platform?

[sky, 2014/04/09 16:49:36]

If unsure, try it out. We need a wallpaper to work when running ash_shell on
windows too.

+#endif
 
   ash::Shell::GetPrimaryRootWindow()->GetHost()->Show();
 }