Cleanup: Get rid of LayoutBlock::offsetFromLogicalTopOfFirstPage().

Cleanup: Get rid of LayoutBlock::offsetFromLogicalTopOfFirstPage().

Fold its contents into LayoutBox::offsetFromLogicalTopOfFirstPage() and make
that one non-virtual. Some non-blocks (e.g. table rows and sections) do
establish layout states, so we cannot just unconditionally jump to the
containing block.

Currently offsetFromLogicalTopOfFirstPage() is never called on non-blocks (in
other words, the LayoutBox implementation of the method just sat there doing
nothing but contribute to the binary size), which explains why we had no bugs
because of this. I expect that non-blocks will call this method in the near
future, though.

R=jchaffraix@chromium.org,leviw@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=195709

[leviw_travelin_and_unemployed, 2015-05-21 17:34:56]

The CQ bit was checked by leviw@chromium.org

[leviw_travelin_and_unemployed, 2015-05-21 17:34:56]

lgtm

Heck yeah!

[commit-bot: I haz the power, 2015-05-21 17:35:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1154493002/1

[commit-bot: I haz the power, 2015-05-21 17:38:29]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=195709