Add infrastructure for partial layouts

Source/core/rendering/RenderRubyBase.h

Index: Source/core/rendering/RenderRubyBase.h
diff --git a/Source/core/rendering/RenderRubyBase.h b/Source/core/rendering/RenderRubyBase.h
index 4d1f56db73d13d0cc6103be68a75a58ead1067a4..5041f07235b47d681427480c3eff5cc943e4ebd1 100644
--- a/Source/core/rendering/RenderRubyBase.h
+++ b/Source/core/rendering/RenderRubyBase.h
@@ -55,6 +55,8 @@ private:
     virtual ETextAlign textAlignmentForLine(bool endsWithSoftBreak) const;
     virtual void adjustInlineDirectionLineBounds(int expansionOpportunityCount, float& logicalLeft, float& logicalWidth) const;
 
+    virtual bool supportsPartialLayout() const OVERRIDE { return false; }
+
     void moveChildren(RenderRubyBase* toBase, RenderObject* beforeChild = 0);
     void moveInlineChildren(RenderRubyBase* toBase, RenderObject* beforeChild = 0);
     void moveBlockChildren(RenderRubyBase* toBase, RenderObject* beforeChild = 0);