Remove background obscuration checks.

sky/engine/core/rendering/RenderBox.h

Index: sky/engine/core/rendering/RenderBox.h
diff --git a/sky/engine/core/rendering/RenderBox.h b/sky/engine/core/rendering/RenderBox.h
index 9e2f74294195ea35fd163aa996a421deeef0a138..87f243b0fc8f4c138a6f93b29d6f1285b822f2cc 100644
--- a/sky/engine/core/rendering/RenderBox.h
+++ b/sky/engine/core/rendering/RenderBox.h
@@ -79,8 +79,6 @@ public:
         return NoLayer;
     }
 
-    virtual bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const override;
-
     // Use this with caution! No type checking is done!
     RenderBox* firstChildBox() const;
     RenderBox* lastChildBox() const;
@@ -483,11 +481,6 @@ protected:
     virtual void styleDidChange(StyleDifference, const RenderStyle* oldStyle) override;
     virtual void updateFromStyle() override;
 
-    // Returns false if it could not cheaply compute the extent (e.g. fixed background), in which case the returned rect may be incorrect.
-    bool getBackgroundPaintedExtent(LayoutRect&) const;
-    virtual bool foregroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect, unsigned maxDepthToTest) const;
-    virtual bool computeBackgroundIsKnownToBeObscured() override;
-
     void paintBackground(const PaintInfo&, const LayoutRect&, const Color& backgroundColor, BackgroundBleedAvoidance = BackgroundBleedNone);
 
     void paintFillLayer(const PaintInfo&, const Color&, const FillLayer&, const LayoutRect&, BackgroundBleedAvoidance, RenderObject* backgroundObject, bool skipBaseColor = false);