Remove RenderImage::styleDidChange.

This simply calls its superclass since about four months ago.
https://codereview.chromium.org/129873009/

Review URL: https://codereview.chromium.org/339753002

git-svn-id: svn://svn.chromium.org/blink/trunk@176260 bbb929c8-8fbe-4397-9dbb-9b2b20218538