 <p>
      If this directive is used on a file that doesn't currently have a content
      overlay, it has no effect.
    </p>
    <object>
      <field name="type" value="remove">
        <ref>String</ref>
      </field>
    </object>
  </type>
  <type name="SourceChange">
    <p>
      A description of a set of edits that implement a single conceptual change.
    </p>
    <object>
      <field name="message">
        <ref>String</ref>
        <p>
          A human-readable description of the change to be 