Delete remaining masks dead code.

sky/engine/core/rendering/RenderObject.h

Index: sky/engine/core/rendering/RenderObject.h
diff --git a/sky/engine/core/rendering/RenderObject.h b/sky/engine/core/rendering/RenderObject.h
index d85619a011672e6291311ef8d8a36f752d1be737..d097263f0496947625c7df6a88e455a29cf86ead 100644
--- a/sky/engine/core/rendering/RenderObject.h
+++ b/sky/engine/core/rendering/RenderObject.h
@@ -372,7 +372,6 @@ public:
     bool hasClipOrOverflowClip() const { return hasClip() || hasOverflowClip(); }
 
     bool hasTransform() const { return m_bitfields.hasTransform(); }
-    bool hasMask() const { return style() && style()->hasMask(); }
     bool hasClipPath() const { return style() && style()->clipPath(); }
     bool hasHiddenBackface() const { return style() && style()->backfaceVisibility() == BackfaceVisibilityHidden; }
 
@@ -626,7 +625,7 @@ public:
     bool shouldUseTransformFromContainer(const RenderObject* container) const;
     void getTransformFromContainer(const RenderObject* container, const LayoutSize& offsetInContainer, TransformationMatrix&) const;
 
-    bool createsGroup() const { return isTransparent() || hasMask() || hasFilter(); }
+    bool createsGroup() const { return isTransparent() || hasFilter(); }
 
     virtual void addFocusRingRects(Vector<IntRect>&, const LayoutPoint& /* additionalOffset */, const RenderLayerModelObject* /* paintContainer */ = 0) const { };