blink: Add backdrop-filter support

Source/core/css/CSSComputedStyleDeclaration.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
@@ skipping 201 matching lines @@
     CSSPropertyWebkitColumnBreakBefore,
     CSSPropertyWebkitColumnBreakInside,
     CSSPropertyWebkitColumnCount,
     CSSPropertyWebkitColumnGap,
     CSSPropertyWebkitColumnRuleColor,
     CSSPropertyWebkitColumnRuleStyle,
     CSSPropertyWebkitColumnRuleWidth,
     CSSPropertyWebkitColumnSpan,
     CSSPropertyWebkitColumnWidth,
     CSSPropertyWebkitFilter,
+    CSSPropertyBackdropFilter,
     CSSPropertyAlignContent,
     CSSPropertyAlignItems,
     CSSPropertyAlignSelf,
     CSSPropertyFlexBasis,
     CSSPropertyFlexGrow,
     CSSPropertyFlexShrink,
     CSSPropertyFlexDirection,
     CSSPropertyFlexWrap,
     CSSPropertyJustifyContent,
     CSSPropertyWebkitFontSmoothing,
@@ skipping 239 matching lines @@
     case CSSPropertyTransform:
     case CSSPropertyTranslate:
     case CSSPropertyRotate:
     case CSSPropertyScale:
     case CSSPropertyTransformOrigin:
     case CSSPropertyMotionPath:
     case CSSPropertyMotionOffset:
     case CSSPropertyMotionRotation:
     case CSSPropertyWidth:
     case CSSPropertyWebkitFilter:
+    case CSSPropertyBackdropFilter:
     case CSSPropertyX:
     case CSSPropertyY:
     case CSSPropertyRx:
     case CSSPropertyRy:
         return true;
     case CSSPropertyMargin:
         return layoutObject && layoutObject->isBox()
             && (!style || !style->marginBottom().isFixed() || !style->marginTop().isFixed()
                 || !style->marginLeft().isFixed() || !style->marginRight().isFixed());
     case CSSPropertyMarginLeft:
@@ skipping 201 matching lines @@
     exceptionState.throwDOMException(NoModificationAllowedError, "These styles are computed, and therefore the '" + getPropertyNameString(id) + "' property is read-only.");
 }
 
 DEFINE_TRACE(CSSComputedStyleDeclaration)
 {
     visitor->trace(m_node);
     CSSStyleDeclaration::trace(visitor);
 }
 
 } // namespace blink