Strip anonymous blocks when change in style removes need for them

When a block element becomes a float or out of flow we should strip
any anonymous blocks wrapping its inline siblings.

BUG=331251

Review URL: https://codereview.chromium.org/253313005

git-svn-id: svn://svn.chromium.org/blink/trunk@174420 bbb929c8-8fbe-4397-9dbb-9b2b20218538