REGRESSION (r166422): All RenderBox objects grew 104 bytes from adding repaint timers.
<https://webkit.org/b/133027>
<rdar://problem/16867410>

Instead of storing a rarely-used repaint timer on every RenderBox, store one
on the RenderView, and keep a hash set of renderers needing repaint.

Renderers get a flag tracking whether they have a pending lazy repaint.
This way we can avoid hash lookups in the common case.

Also added a static assertion to catch RenderBox growing in the future.

Reviewed by Antti Koivisto.

* rendering/RenderBox.cpp:
(WebCore::SameSizeAsRenderBox::~SameSizeAsRenderBox):
(WebCore::RenderBox::RenderBox):
(WebCore::RenderBox::~RenderBox):
(WebCore::RenderBox::paintBoxDecorations):
(WebCore::RenderBox::layoutOverflowRectForPropagation):
* rendering/RenderBox.h:
* rendering/RenderElement.cpp:
(WebCore::RenderElement::RenderElement):
* rendering/RenderElement.h:
(WebCore::RenderElement::setRenderBoxNeedsLazyRepaint):
(WebCore::RenderElement::renderBoxNeedsLazyRepaint):
* rendering/RenderView.cpp:
(WebCore::RenderView::RenderView):
(WebCore::RenderView::scheduleLazyRepaint):
(WebCore::RenderView::unscheduleLazyRepaint):
(WebCore::RenderView::lazyRepaintTimerFired):
* rendering/RenderView.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@168993 268f45cc-cd09-0410-ab3c-d52691b4dbfc