ScrollableArea should lazily allocate ScrollAnimator to save memory.
<rdar://problem/9365401>
Created attachment 92516 [details] Patch
Comment on attachment 92516 [details] Patch Attachment 92516 [details] did not pass chromium-ews (chromium-xvfb): Output: http://queues.webkit.org/results/8587230
Checked in with fixes: http://trac.webkit.org/changeset/85955