Remove RenderSelectionInfo

The class was misguided and only needed because
we generated the invalidations using this code
path before https://codereview.chromium.org/665673004

BUG=407416

Review URL: https://codereview.chromium.org/696703005

git-svn-id: svn://svn.chromium.org/blink/trunk@185307 bbb929c8-8fbe-4397-9dbb-9b2b20218538