Revert "Change Aura desktop background behavior."
Revert "Change Aura desktop background behavior."

This reverts commit 7fdf4eb7cd05b725d246ef8be99eb43784ed5ad3.

R=saintlou@chromium.org
BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/9549024

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@124326 0039d316-1c4b-4281-b951-d872f2087c98

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