Remove unused mask and background methods.

Source/core/rendering/style/RenderStyle.h

Index: Source/core/rendering/style/RenderStyle.h
diff --git a/Source/core/rendering/style/RenderStyle.h b/Source/core/rendering/style/RenderStyle.h
index 28240c60579b2751e4e5c482b05780f1adcd09ae..8fe1498fd6ee7ec2f81030d5726cd31e70f87dd3 100644
--- a/Source/core/rendering/style/RenderStyle.h
+++ b/Source/core/rendering/style/RenderStyle.h
@@ -1132,9 +1132,6 @@ public:
     void setWordSpacing(float);
     void setLetterSpacing(float);
 
-    void clearBackgroundLayers() { m_background.access()->m_background = FillLayer(BackgroundFillLayer); }
-    void inheritBackgroundLayers(const FillLayer& parent) { m_background.access()->m_background = parent; }
-
     void adjustBackgroundLayers()
     {
         if (backgroundLayers()->next()) {
@@ -1143,9 +1140,6 @@ public:
         }
     }
 
-    void clearMaskLayers() { rareNonInheritedData.access()->m_mask = FillLayer(MaskFillLayer); }
-    void inheritMaskLayers(const FillLayer& parent) { rareNonInheritedData.access()->m_mask = parent; }
-
     void adjustMaskLayers()
     {
         if (maskLayers()->next()) {