Add documentation for filtered events.

chrome/common/extensions/docs/template/api_template.html

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                 <div jsdisplay="extraParameters && extraParameters.length > 0">
                   <h4>Extra parameters to addListener</h4>
                   <dl>
                     <div jsselect="extraParameters">
                       <div transclude="valueTemplate">
                       </div>
                     </div>
                   </dl>
                 </div>
 
+                <!-- FILTERS -->
+                <div jsdisplay="filters && filters.length > 0">
+                  <h4>Filters</h4>
+                  <dl>
+                    <div jsselect="filters">
+                      <div transclude="valueTemplate">
+                      </div>
+                    </div>
+                  </dl>
+                </div>
+
                 <!-- LISTENER RETURN VALUE -->
                 <h4 jsdisplay="returns">Listener returns</h4>
                 <dl>
                   <div jsselect="returns">
                     <div transclude="valueTemplate">
                     </div>
                   </div>
                 </dl>
 
               </div> <!-- /description -->
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