Make download shelf themeable.
Make download shelf themeable.

BUG=none
TEST=Install a theme, notice that the download shelf now at least somewhat fits with the new theme.
Review URL: http://codereview.chromium.org/159126

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@21205 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser