Remove background obscuration checks.

sky/engine/core/rendering/style/StyleDifference.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SKY_ENGINE_CORE_RENDERING_STYLE_STYLEDIFFERENCE_H_
 #define SKY_ENGINE_CORE_RENDERING_STYLE_STYLEDIFFERENCE_H_
 
 #include "sky/engine/wtf/Assertions.h"
 
 namespace blink {
 
 class StyleDifference {
 public:
     enum PropertyDifference {
         TransformChanged = 1 << 0,
         OpacityChanged = 1 << 1,
         ZIndexChanged = 1 << 2,
         FilterChanged = 1 << 3,
     };
 
     StyleDifference()
-        : m_needsPaintInvalidation(false)
-        , m_layoutType(NoLayout)
+        : m_layoutType(NoLayout)
         , m_propertySpecificDifferences(0)
     { }
 
-    bool needsPaintInvalidation() const { return m_needsPaintInvalidation; }
-    void setNeedsPaintInvalidation()
-    {
-        m_needsPaintInvalidation = true;
-    }
-
     bool needsLayout() const { return m_layoutType != NoLayout; }
     void clearNeedsLayout() { m_layoutType = NoLayout; }
 
     // The offset of this positioned object has been updated.
     bool needsPositionedMovementLayout() const { return m_layoutType == PositionedMovement; }
     void setNeedsPositionedMovementLayout()
     {
         ASSERT(!needsFullLayout());
         m_layoutType = PositionedMovement;
     }
 
     bool needsFullLayout() const { return m_layoutType == FullLayout; }
     void setNeedsFullLayout() { m_layoutType = FullLayout; }
 
     bool transformChanged() const { return m_propertySpecificDifferences & TransformChanged; }
     void setTransformChanged() { m_propertySpecificDifferences |= TransformChanged; }
 
     bool opacityChanged() const { return m_propertySpecificDifferences & OpacityChanged; }
     void setOpacityChanged() { m_propertySpecificDifferences |= OpacityChanged; }
 
     bool zIndexChanged() const { return m_propertySpecificDifferences & ZIndexChanged; }
     void setZIndexChanged() { m_propertySpecificDifferences |= ZIndexChanged; }
 
     bool filterChanged() const { return m_propertySpecificDifferences & FilterChanged; }
     void setFilterChanged() { m_propertySpecificDifferences |= FilterChanged; }
 
 private:
-    unsigned m_needsPaintInvalidation : 1;
-
     enum LayoutType {
         NoLayout = 0,
         PositionedMovement,
         FullLayout
     };
     unsigned m_layoutType : 2;
 
     unsigned m_propertySpecificDifferences : 5;
 };
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_RENDERING_STYLE_STYLEDIFFERENCE_H_