Created attachment 227808 [details] patch Synchronous messages between the WebProcess and the PluginProcess keep the PluginProcess awake even in the background. Since we believe that AppSleep assertions are only necessary during user activity, drawing, or audio playing and those are all covered elsewhere don't take an assertion while conveying sync messages.
Comment on attachment 227808 [details] patch oops wrong patch
Created attachment 227979 [details] real patch
http://trac.webkit.org/changeset/166444