Update comment in NodeRenderingTraversal::parent

This comment came from long ago when we were still working on lazy attach,
now it seems the thing blocking the ASSERT is that some callers of
NodeRenderingTraversal::parent are in places where distribution might be
dirty, ex. HTMLSummaryElement::detailsElement().

Perhaps we should add calls to updateDistributionForNodeIfNeeded to those
callers and then add the assert. For now this patch just fixes the comment.

Review URL: https://codereview.chromium.org/70173004

git-svn-id: svn://svn.chromium.org/blink/trunk@162069 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Removed unused function declaration and member variable from RenderText

R=abarth@chromium.org
BUG=

Review URL: https://codereview.chromium.org/71163007

git-svn-id: svn://svn.chromium.org/blink/trunk@162070 bbb929c8-8fbe-4397-9dbb-9b2b20218538