blink: Add backdrop-filter support

Source/core/animation/ElementAnimations.cpp

Index: Source/core/animation/ElementAnimations.cpp
diff --git a/Source/core/animation/ElementAnimations.cpp b/Source/core/animation/ElementAnimations.cpp
index c11f5405e2d0589aed0b168bfa8eca0301639884..ec24307de18ffad33d6c2646facc577c468c556a 100644
--- a/Source/core/animation/ElementAnimations.cpp
+++ b/Source/core/animation/ElementAnimations.cpp
@@ -67,6 +67,8 @@ void ElementAnimations::updateAnimationFlags(ComputedStyle& style)
                 style.setHasCurrentTransformAnimation(true);
             if (effect.affects(PropertyHandle(CSSPropertyWebkitFilter)))
                 style.setHasCurrentFilterAnimation(true);
+            if (effect.affects(PropertyHandle(CSSPropertyBackdropFilter)))
+                style.setHasCurrentBackdropFilterAnimation(true);
         }
     }
 
@@ -76,6 +78,8 @@ void ElementAnimations::updateAnimationFlags(ComputedStyle& style)
         style.setIsRunningTransformAnimationOnCompositor(m_defaultStack.hasActiveAnimationsOnCompositor(CSSPropertyTransform));
     if (style.hasCurrentFilterAnimation())
         style.setIsRunningFilterAnimationOnCompositor(m_defaultStack.hasActiveAnimationsOnCompositor(CSSPropertyWebkitFilter));
+    if (style.hasCurrentBackdropFilterAnimation())
+        style.setIsRunningBackdropFilterAnimationOnCompositor(m_defaultStack.hasActiveAnimationsOnCompositor(CSSPropertyBackdropFilter));
 }
 
 void ElementAnimations::restartAnimationOnCompositor()