[New Multicolumn] boundingBoxForCompositingOverlapTest() needs to use fragmentsBoundingBox().

[New Multicolumn] boundingBoxForCompositingOverlapTest() needs to use fragmentsBoundingBox().

Bounding boxes are visual, so we need to translate a flow thread
rectangle to the union of each visual fragment in each column that the
layer occurs. This means that flippedLogicalBoundingBox() won't do. Nor
will physicalBoundingBox(), which, despite its name, isn't "physical"
enough for multicol. In our case, flippedLogicalBoundingBox() and
physicalBoundingBox() would behave identically anyway, since the
ancestor layer is the same as this layer (and physicalBoundingBox()
only adds the offset from this layer to the ancestor).

BUG=359877
R=jchaffraix@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184670

[Julien - ping for review, 2014-10-29 17:52:48]

lgtm.

The description is pretty weird: boundingBox / physicalBoundingBox are based on
flippedLogicalBoundingBox, especially since your test doesn't care that it's
logical (FIXME: you should have a vertical writing mode test).

I would rather explain how the box offset was wrong with fragments.

[mstensho (USE GERRIT), 2014-10-30 19:48:58]

On 2014/10/29 17:52:48, Julien Chaffraix - PST wrote:
> lgtm.
> 
> The description is pretty weird: boundingBox / physicalBoundingBox are based
on
> flippedLogicalBoundingBox, especially since your test doesn't care that it's
> logical (FIXME: you should have a vertical writing mode test).
> 
> I would rather explain how the box offset was wrong with fragments.

I've improved the description and added vertical writing mode tests. The one for
vertical-rl actually fails, but that's not related to this CL. So I've added it
to TestExpectations and I'll file a fix once this CL has landed.

[mstensho (USE GERRIT), 2014-10-30 19:49:04]

The CQ bit was checked by mstensho@opera.com

[commit-bot: I haz the power, 2014-10-30 19:50:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/655003005/40001

[commit-bot: I haz the power, 2014-10-30 21:37:33]

Committed patchset #3 (id:40001) as 184670