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

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241505 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241505
Fix selecting files in Chrome OS.

One of recent CLs being part of a bigger refactoring process instroduced a regression caused by using selection.entries, however selection.entries is not used at this stage, yet.
This CL fixes this issue by converting selection.urls to entries and then using the Entry[] collection to fetch metadata.

TEST=Tested manually.
BUG=329332

Review URL: https://codereview.chromium.org/103443006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241506 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241506