Remove assorted dead paint invalidation code.

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 1bef0577a32385e30d70153e129420eb195e16ea..9e2f74294195ea35fd163aa996a421deeef0a138 100644
--- a/sky/engine/core/rendering/RenderBox.h
+++ b/sky/engine/core/rendering/RenderBox.h
@@ -53,18 +53,13 @@ public:
         : m_inlineBoxWrapper(0)
         , m_overrideLogicalContentHeight(-1)
         , m_overrideLogicalContentWidth(-1)
-        , m_previousBorderBoxSize(-1, -1)
     {
     }
 
     // For inline replaced elements, the inline box that owns us.
     InlineBox* m_inlineBoxWrapper;
-
     LayoutUnit m_overrideLogicalContentHeight;
     LayoutUnit m_overrideLogicalContentWidth;
-
-    // Set by RenderBox::updatePreviousBorderBoxSizeIfNeeded().
-    LayoutSize m_previousBorderBoxSize;
 };
 
 
@@ -566,9 +561,6 @@ private:
         return *m_rareData.get();
     }
 
-    void savePreviousBorderBoxSizeIfNeeded();
-    LayoutSize computePreviousBorderBoxSize(const LayoutSize& previousBoundsSize) const;
-
     bool logicalHeightComputesAsNone(SizeType) const;
 
     bool isBox() const = delete; // This will catch anyone doing an unnecessary check.