CSS: Add a property cascading pass to style application.

CSS: Add a property cascading pass to style application.
<https://webkit.org/b/125213>

Add an intermediate pass to style application where we cascade all
style properties to figure out their final values before starting
to build RenderStyles.

This opens up various opportunities for further optimization.

Reviewed by Antti Koivisto.

* css/StyleResolver.cpp:
(WebCore::StyleResolver::CascadedProperties::Property::Property):
(WebCore::StyleResolver::CascadedProperties::CascadedProperties):
(WebCore::StyleResolver::CascadedProperties::property):
(WebCore::StyleResolver::CascadedProperties::set):
(WebCore::StyleResolver::CascadedProperties::addStyleProperties):
(WebCore::StyleResolver::CascadedProperties::addMatches):
(WebCore::StyleResolver::CascadedProperties::Property::apply):

    Added. CascadedProperties is something of a container class
    that takes CSS property/value/linkMatchType as input and boils
    them down to the final values that will actually be used.

    Most properties are poked into an unfancy array where latest
    is greatest (unless !important, of course.) Some properties are
    queued up to be applied in parse order, more on that below.

(WebCore::StyleResolver::applyCascadedProperties):
(WebCore::StyleResolver::applyMatchedProperties):

    The brains of this patch. applyMatchedProperties() now creates
    a CascadedProperties and uses it to figure out the final values
    and uses applyCascadedProperties() to apply them. Deferred
    properties (parse order) are applied last.

    We may discover during property application that we won't be
    able to use a matched properties cache item. This happens if
    the effective zoom or font changes. If that happens, we start
    the process over, now with the cache disabled. This may need
    some optimization work.

(WebCore::extractDirectionAndWritingMode):

    Directional properties ending in e.g -before or -after depend on
    the direction and writing mode in effect, so we must begin with
    resolving those properties before doing the full cascade.

    This is done by simply walking the set of matched properties and
    manually applying '-webkit-writing-mode' and 'direction'.

    If this starts showing up in profiles, we can easily cache some
    of the information in e.g RuleData to avoid the traversal here.

(WebCore::elementTypeHasAppearanceFromUAStyle):

    To determine whether a form element is styled beyond the default
    UA style sheet, StyleResolver caches the border and background
    values from RenderStyle after applying the UA style sheet.

    Those values are then compared against after all style is applied
    and if some (platform-dependent) values differ, the element is
    considered "styled."

    This really only affects elements with -webkit-appearance values
    in the default UA style sheet, so this function determines if an
    element should take the goofy slow path for this.

(WebCore::shouldApplyPropertyInParseOrder):
(WebCore::StyleResolver::CascadedProperties::setDeferred):
(WebCore::StyleResolver::CascadedProperties::applyDeferredProperties):

    Some CSS properties will write to the same RenderStyle fields when
    applied, so in order to maintain previous behavior, we must apply
    them in the order they were parsed.

    We accomplish this by keeping an ordered queue of such properties
    to apply separately after all the other properties.

(WebCore::StyleResolver::CascadedProperties::setPropertyInternal):

    Helper for poking values into a CascadedProperties::Property.

* css/StyleResolver.h:
(WebCore::StyleResolver::state):

    Expose the StyleResolver::State so CascadedProperties can access it.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@160806 268f45cc-cd09-0410-ab3c-d52691b4dbfc