xtension cache control directives.</div>
<dl class="notes">
<dt>Returns:</dt>
<dd>a mutable map of cache control extension names and their values. If a key has a null value, it will appear as
 a bare directive. If a key has a value that contains no whitespace then the directive will appear as a simple
 name=value pair. If a key has a value that contains whitespace then the directive will appear as a quoted
 name="value" pair.</dd>
<dt>See Also:</dt>
<dd>
<ul class="see-list">
<li><a href="http://www.w3.org/