Remove custom style building functions for 'clip'.

The property 'clip' is (with some modifications) compatible with the
apply_auto-properties.

Changes in this commit:

 * Use apply_auto + converter instead of custom building functions.
 * StyleVisualData::hasClip -> hasAutoClip (meaning reversed).
 * Remove unnecessary RenderStyle::setClip*-functions.

Review URL: https://codereview.chromium.org/462133002

git-svn-id: svn://svn.chromium.org/blink/trunk@180465 bbb929c8-8fbe-4397-9dbb-9b2b20218538