Factored common page set management into a new PageSet class
Created attachment 76929 [details] Patch
Attachment 76929 [details] did not build on qt: Build output: http://queues.webkit.org/results/7253019
Created attachment 76933 [details] Patch
Comment on attachment 76933 [details] Patch r=me if you change the name to PageBlock.
Committed r74357: <http://trac.webkit.org/changeset/74357>