13. A computer comprising: a storage device; and hardware processor, operably: provide an overlay client to a first user in an online social network, the overlay client to provide an interface between a service application on the computer and the online social network; identify a set of content sources associated with the first user comprising the storage device obtain via the overlay client, content from the set of content sources; receive a poll request associated with the content from a message server, wherein the poll request comprises an instruction to perform a client-side data scraping operation; originate a data request in response to the client-side data scraping operation; cause the service application to submit the data request to the online social network in view of the poll request; and receive a message associated with a second user from the online social network-that corresponds to an activity of the online social network, wherein the first user has previously engaged with the online social network, and wherein the activity is of interest to the first user.
13. A computer comprising: a storage device; and hardware processor, operably: provide an overlay client to a first user in an online social network, the overlay client to provide an interface between a service application on the computer and the online social network; identify a set of content sources associated with the first user comprising the storage device obtain via the overlay client, content from the set of content sources; receive a poll request associated with the content from a message server, wherein the poll request comprises an instruction to perform a client-side data scraping operation; originate a data request in response to the client-side data scraping operation; cause the service application to submit the data request to the online social network in view of the poll request; and receive a message associated with a second user from the online social network-that corresponds to an activity of the online social network, wherein the first user has previously engaged with the online social network, and wherein the activity is of interest to the first user. 14. The computer of claim 13 , wherein the hardware processor is to display information that identifies the content in a display device.