Remove wrong commented out code from RenderLayer::updateLayerPositionsAfterScroll

Remove wrong commented out code from RenderLayer::updateLayerPositionsAfterScroll

This comment is about ASSERTing the consistency of state that no long exists.
Also, remove m_canSkipRepaintRectsUpdateOnScroll because it's just
renderer()->isTableCell().

R=esprehn@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177129

[esprehn, 2014-06-27 18:11:52]

On 2014/06/27 18:10:32, abarth wrote:

This lgtm, but I wonder why table cells are special.

[abarth-chromium, 2014-06-27 18:47:33]

On 2014/06/27 at 18:11:52, esprehn wrote:
> On 2014/06/27 18:10:32, abarth wrote:
> 
> This lgtm, but I wonder why table cells are special.

I suspect their repaint containers are always close by and the update is always
a no-op.  If we track the repaint container as we walk down the tree, I suspect
we can make that optimization generic by only applying it when the thing that
scrolled is under the repaint container.

[abarth-chromium, 2014-06-27 20:12:26]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-06-27 20:12:47]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/abarth@chromium.org/356123004/1

[abarth-chromium, 2014-06-27 20:34:54]

Committed patchset #1 manually as r177129 (presubmit successful).