This improvement adds a portal level polling mechanism that portlets can use. More specifically, the chat portlet no longer does it's own polling and has been updated to use the new polling mechanism.
liferay-portlet.xml now has:
The poller-processor-class value must be a class that implements
com.liferay.portal.kernel.poller.PollerProcessor and is triggered by the
notified of data changes. See the Chat portlet for a real world implementation.
<!ELEMENT poller-processor-class (#PCDATA)>
Implementing this class abstracts out polling mechanism by allowing the portal to route messages between a web site and a portlet. It allows notifications to go both ways. The implementation of the polling itself can be done either via regular polls or long polls or anything else. This refactor abstracts that problem out.