Web Animations CSS: Alpha order of the CSS property switch list

AnimatedStyleBuilder.cpp appears to maintain an alpha sorted switch
list. Move CSSPropertyListStyleImage after CSSPropertyLeft.

Review URL: https://chromiumcodereview.appspot.com/23876013

git-svn-id: svn://svn.chromium.org/blink/trunk@157816 bbb929c8-8fbe-4397-9dbb-9b2b20218538