New scrollbar images

BUG=333499
TEST=none
R=oshima@chromium.org
TBR=oshima@chromium.org

Review URL: https://codereview.chromium.org/155973007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250056 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250056