Fix the crash in DesktopBackgroundView::OnPaint

chrome/browser/chromeos/extensions/wallpaper_private_api.h

Index: chrome/browser/chromeos/extensions/wallpaper_private_api.h
diff --git a/chrome/browser/chromeos/extensions/wallpaper_private_api.h b/chrome/browser/chromeos/extensions/wallpaper_private_api.h
index f640cad77cd94cb16cac2561fb9e383eea86f8d1..9b9ed1f367ec7f270b5dce7a2aee3bb6af3bd19f 100644
--- a/chrome/browser/chromeos/extensions/wallpaper_private_api.h
+++ b/chrome/browser/chromeos/extensions/wallpaper_private_api.h
@@ -63,12 +63,13 @@ class WallpaperSetWallpaperFunction : public WallpaperFunctionBase {
   void SaveToFile();
 
   // Sets wallpaper to the decoded image.
-  void SetDecodedWallpaper();
+  void SetDecodedWallpaper(scoped_ptr<gfx::ImageSkia> wallpaper);
 
   // Layout of the downloaded wallpaper.
   ash::WallpaperLayout layout_;
 
-  // The decoded wallpaper.
+  // The decoded wallpaper. It may accessed from UI thread to set wallpaper or
+  // FILE thread to resize and save wallpaper to disk.
   gfx::ImageSkia wallpaper_;
 
   // Email address of logged in user.