Revert of Don't rely on values computed as a side effect of paint. (https://codereview.chromium.org/208203002/)

Reason for revert:
Looks like this is causing ASSERTs due to calling layout-dependent code at the wrong time: https://code.google.com/p/chromium/issues/detail?id=355277

Original issue's description:
> Don't rely on values computed as a side effect of paint.
> 
> Contrary to the assertions on the bug, the current code is correct. As
> the user changes the selection, there will naturally be a visual
> affordance to indicate the selection changes. By the time we scroll,
> RL::hasBlockSelectionGapsBounds will be current and correct.
> 
> That said, the hope is that in the future paint will have no side
> effects at all, nor do we want layout tests to require repaints during
> their execution. So even if this is technically correct it's undesirable
> on a number of levels.
> 
> This cl replaces the use of hasBlockSelectionGapsBounds with non-paint
> related code (in fact, that function could be removed entirely).
> 
> R=abarth@chromium.org
> BUG=353827
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=169752

TBR=abarth@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=353827

Review URL: https://codereview.chromium.org/209543002

git-svn-id: svn://svn.chromium.org/blink/trunk@169813 bbb929c8-8fbe-4397-9dbb-9b2b20218538