Reviewed by Dimitri Glazkov.

        Convert <progress> shadow DOM to a DOM-based shadow.
        https://bugs.webkit.org/show_bug.cgi?id=50660

        * Removed RenderProgress::m_valuePart, moved the shadow node
          to the shadow root of HTMLProgressElement.
        * Removed hard-coded pseudo ID for -webkit-progress-bar-value.
          ProgressBarValueElement is defined only for overriding
          shadowPseudoId().

        No new tests. No behavioral change.

        * css/CSSSelector.cpp:
        (WebCore::CSSSelector::pseudoId):
        (WebCore::nameToPseudoTypeMap):
        (WebCore::CSSSelector::extractPseudoType):
        * css/CSSSelector.h:
        * html/HTMLProgressElement.cpp:
        (WebCore::ProgressBarValueElement::ProgressBarValueElement):
        (WebCore::ProgressBarValueElement::shadowPseudoId):
        (WebCore::ProgressBarValueElement::create):
        (WebCore::HTMLProgressElement::parseMappedAttribute):
        (WebCore::HTMLProgressElement::attach):
        (WebCore::HTMLProgressElement::valuePart):
        (WebCore::HTMLProgressElement::didElementStateChange):
        (WebCore::HTMLProgressElement::createShadowSubtreeIfNeeded):
        * html/HTMLProgressElement.h:
        * rendering/RenderProgress.cpp:
        (WebCore::RenderProgress::~RenderProgress):
        (WebCore::RenderProgress::updateFromElement):
        (WebCore::RenderProgress::layoutParts):
        (WebCore::RenderProgress::shouldHaveParts):
        (WebCore::RenderProgress::valuePart):
        * rendering/RenderProgress.h:
        * rendering/style/RenderStyleConstants.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@77107 268f45cc-cd09-0410-ab3c-d52691b4dbfc