Remove the ENABLE_IFRAME_SEAMLESS compile-time flag.

Source/WebCore/css/SelectorChecker.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 678 matching lines @@
             return element->document()->isAnimatingFullScreen();
         case CSSSelector::PseudoFullScreenAncestor:
             return element->containsFullScreenElement();
         case CSSSelector::PseudoFullScreenDocument:
             // While a Document is in the fullscreen state, the 'full-screen-document' pseudoclass applies
             // to all elements of that Document.
             if (!element->document()->webkitIsFullScreen())
                 return false;
             return true;
 #endif
-#if ENABLE(IFRAME_SEAMLESS)
         case CSSSelector::PseudoSeamlessDocument:
             // While a document is rendered in a seamless iframe, the 'seamless-document' pseudoclass applies
             // to all elements of that Document.
             return element->document()->shouldDisplaySeamlesslyWithParent();
-#endif
         case CSSSelector::PseudoInRange:
             if (!element)
                 return false;
             element->document()->setContainsValidityStyleRules();
             return element->isInRange();
         case CSSSelector::PseudoOutOfRange:
             if (!element)
                 return false;
             element->document()->setContainsValidityStyleRules();
             return element->isOutOfRange();
@@ skipping 188 matching lines @@
     return element->focused() && isFrameFocused(element);
 }
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, PseudoId&, const DOMSiblingTraversalStrategy&) const;
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, PseudoId&, const ShadowDOMSiblingTraversalStrategy&) const;
 
 }