Special list-item counter starts from an incorrect number for ::before and ::after

Special list-item counter starts from an incorrect number for ::before and ::after
https://bugs.webkit.org/show_bug.cgi?id=181084

Reviewed by Zalan Bujtas.

Source/WebCore:

Test: fast/css/counters/counter-list-item.html

* Sources.txt: Removed CounterDirectives.cpp.
* WebCore.xcodeproj/project.pbxproj: Ditto.

* css/CSSComputedStyleDeclaration.cpp:
(WebCore::counterToCSSValue): Updated for changes to the CounterDirectives struct.
* css/StyleBuilderCustom.h:
(WebCore::StyleBuilderCustom::applyInheritCounter): Ditto.
(WebCore::StyleBuilderCustom::applyValueCounter): Ditto.

* html/HTMLLIElement.cpp:
(WebCore::HTMLLIElement::parseValue): Call setExplicitValue(std::nullopt) instead
of clearExplicitValue since we are using std::optional now.

* rendering/RenderCounter.cpp:
(WebCore::listItemCounterDirectives): Added. Computes the counter directives that
express the effects on the list-item counter from list item and list elements.
Used something as close to what the CSS 3 draft says as possible. This uses a
negative increment when creating a list to counteract the positive increment done
by a list element, except in the case of an unordered list. This is where the bug
fix actually lies. Also fixed handling of reversed ordered lists at the same time.
(WebCore::planCounter): Refactored to use the function above. Also changed the
code to pay attention to both the counter directives and the implicit ones from
list item and list elements, getting as close as possible to what the specification
seems to call for.

* rendering/RenderListItem.cpp:
(WebCore::RenderListItem::RenderListItem): Since we are using std::optional and no
longer using bit fields, simplified the constructor for each list item.
(WebCore::RenderListItem::calcValue const): Deleted.
(WebCore::RenderListItem::updateValueNow const): Merged in all the code from the
old calcValue function, but it is also simpler now since m_value is std::optional.
(WebCore::RenderListItem::updateValue): Updated to use std::optional.
(WebCore::RenderListItem::setExplicitValue): Ditto.
(WebCore::RenderListItem::clearExplicitValue): Deleted.
(WebCore::RenderListItem::updateListMarkerNumbers): Updated to use std::optional.
(WebCore::RenderListItem::isInReversedOrderedList const): Added. This is used by
the counter code so it can decrement instead of incrementing.

* rendering/RenderListItem.h: Updated to use std::optional. Also marked functions
final instead of override and initialized m_notInList after making it not be a
bitfield any more.

* rendering/style/CounterDirectives.cpp: Removed.
* rendering/style/CounterDirectives.h: Removed most of the CounterDirectives
class and replaced it with a struct with two std::optional. Added an addClamped
function so the counter code can share it with the addIncrementValue function.
If we want to make a faster version that doesn't use double, we can come back
and do that. Also moved the == function to the header since the implementation
is so trivial.

* rendering/style/StyleAllInOne.cpp: Removed CounterDirectives.cpp.

* rendering/style/StyleRareNonInheritedData.cpp:
(WebCore::StyleRareNonInheritedData::StyleRareNonInheritedData): Updated to
use std::make_unique directly instead of using a clone function.

LayoutTests:

* fast/css/counters/counter-list-item-expected.html: Added.
* fast/css/counters/counter-list-item.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@226613 268f45cc-cd09-0410-ab3c-d52691b4dbfc