Check in 2x slider bar resources, also slightly adjust 1x resource files for slider_thumb.png and slider_thumb_disabled.png.

BUG=140077
TBR=sky,oshima

Review URL: https://chromiumcodereview.appspot.com/10824133

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@149500 0039d316-1c4b-4281-b951-d872f2087c98