Revert 227477 "Refactored loading of applications / extensions i..."
as it has introduced data races.
BUG=304180

> Refactored loading of applications / extensions icons.
> Added ImageLoader::LoadExtensionIconAsync() and ImageLoader::LoadExtensionIconDataURLAsync().
> Moved all apps / extension loading code to ImageLoader.
> 
> BUG=297298, 297301, 304180
> 
> Review URL: https://codereview.chromium.org/26161002

TBR=dvh@chromium.org

Review URL: https://codereview.chromium.org/26511002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227520 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227520