Remove RenderFlowThread::offsetFromLogicalTopOfFirstRegion().

Remove RenderFlowThread::offsetFromLogicalTopOfFirstRegion().

What RenderBlock::offsetFromLogicalTopOfFirstPage() does via its
layout state also suffices for flowthread-based multicol.

This also made 'flow thread layout state' vanish into thin air.

R=jchaffraix@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=186532

[mstensho (USE GERRIT), 2014-12-04 15:58:58]

A little more background: What I really wanted to get rid of was "Flow Thread
Layout State", because it caused me some trouble with stuff I was working on.
When I removed that (and the then unused RenderBoxToOffsetMap stuff), I took a
closer look at what was left in
RenderFlowThread::offsetFromLogicalTopOfFirstRegion(). It turned out that most
of it had no coverage from tests, and I couldn't figure out any call sites in
the code that would need anything other than reading out layoutOffset() -
pageOffset() from LayoutState. This method was always called for the block
currently being laid out.

So I decided to remove the whole thing, rather than writing unit tests to
exercise more of this code. Writing layout tests to achieve it would have been
impossible, since no web exposed APIs can take us there.

[Julien - ping for review, 2014-12-04 16:46:19]

lgtm.

It seems like it was some code that made sense for region (you could end up with
content from different sources going into different regions) but doesn't make
sense in a multicol world.

https://codereview.chromium.org/775753002/diff/1/Source/core/rendering/Render...
File Source/core/rendering/RenderBlock.cpp (right):

https://codereview.chromium.org/775753002/diff/1/Source/core/rendering/Render...
Source/core/rendering/RenderBlock.cpp:3648: if (!layoutState) {
ASSERT(layoutState) / RELEASE_ASSERT(layoutState)?

[mstensho (USE GERRIT), 2014-12-04 18:19:43]

Yeah, pretty sure this was written with regions in mind.

https://codereview.chromium.org/775753002/diff/1/Source/core/rendering/Render...
File Source/core/rendering/RenderBlock.cpp (right):

https://codereview.chromium.org/775753002/diff/1/Source/core/rendering/Render...
Source/core/rendering/RenderBlock.cpp:3648: if (!layoutState) {
On 2014/12/04 16:46:19, Julien Chaffraix - PST wrote:
> ASSERT(layoutState) / RELEASE_ASSERT(layoutState)?

Done.

[mstensho (USE GERRIT), 2014-12-04 18:19:49]

The CQ bit was checked by mstensho@opera.com

[commit-bot: I haz the power, 2014-12-04 18:20:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/775753002/20001

[commit-bot: I haz the power, 2014-12-04 19:30:51]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=186532