Introduce :-internal-shadow-host-has-appearance pseudo class, and apply it to METER element.

third_party/WebKit/Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 2747 matching lines @@
 {
     if (ShadowRoot* root = containingShadowRoot()) {
         if (root->type() == ShadowRootType::UserAgent)
             return fastGetAttribute(pseudoAttr);
     }
     return nullAtom;
 }
 
 void Element::setShadowPseudoId(const AtomicString& id)
 {
-    DCHECK_EQ(CSSSelector::parsePseudoType(id, false), CSSSelector::PseudoWebKitCustomElement);
+    DCHECK(CSSSelector::parsePseudoType(id, false) == CSSSelector::PseudoWebKitCustomElement || CSSSelector::parsePseudoType(id, false) == CSSSelector::PseudoBlinkInternalElement);
     setAttribute(pseudoAttr, id);
 }
 
 bool Element::isInDescendantTreeOf(const Element* shadowHost) const
 {
     DCHECK(shadowHost);
     DCHECK(isShadowHost(shadowHost));
 
     for (const Element* ancestorShadowHost = this->shadowHost(); ancestorShadowHost; ancestorShadowHost = ancestorShadowHost->shadowHost()) {
         if (ancestorShadowHost == shadowHost)
@@ skipping 920 matching lines @@
 
 DEFINE_TRACE(Element)
 {
     if (hasRareData())
         visitor->trace(elementRareData());
     visitor->trace(m_elementData);
     ContainerNode::trace(visitor);
 }
 
 } // namespace blink