Revert 241505 "Fix preloading images when copying."

> Fix preloading images when copying.
> 
> The previous fix incorrectly was passing an entry, however the ThumbnailLoader does not work on entries yet.
> This patch fixes this issue by passing an url instead of the entry.
> 
> TEST=Tested manually.
> BUG=328238
> 
> Review URL: https://codereview.chromium.org/117803005

TBR=mtomasz@chromium.org

Review URL: https://codereview.chromium.org/106383005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242509 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242509