Fix cropping cursors in the gallery.

This patch fixes the CSS rules, so they have proper syntax.

TEST=Try to crop, mouse cursors should be visible.
BUG=305087

Review URL: https://codereview.chromium.org/26897006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229723 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229723