fix(material-experimental/mdc-slider): append class to indicate short value indicator text (#23566)
fix(material-experimental/mdc-slider): append class to indicate short value indicator text (#23566)

* This class is only used internally. It is a temporary fix which will be removed
  once the appending of this class is handled by the mdc foundation (cl/388828896).
josephperrott/material2,josephperrott/material2,josephperrott/material2,crisbeto/material2,crisbeto/material2,angular/components,josephperrott/material2,josephperrott/material2,crisbeto/material2,crisbeto/material2,angular/components,angular/components,angular/components