Remove code that is unused after ContextMenu cleanup

Source/core/rendering/RenderBlock.h

Index: Source/core/rendering/RenderBlock.h
diff --git a/Source/core/rendering/RenderBlock.h b/Source/core/rendering/RenderBlock.h
index e02326b895a566a03ba36cfdc10e0f20e931cf7b..a632c62f42ee12b157038c072086080b9317669a 100644
--- a/Source/core/rendering/RenderBlock.h
+++ b/Source/core/rendering/RenderBlock.h
@@ -234,8 +234,6 @@ public:
     RootInlineBox* firstRootBox() const { return static_cast<RootInlineBox*>(firstLineBox()); }
     RootInlineBox* lastRootBox() const { return static_cast<RootInlineBox*>(lastLineBox()); }
 
-    bool containsNonZeroBidiLevel() const;
-
     GapRects selectionGapRectsForRepaint(const RenderLayerModelObject* repaintContainer);
     LayoutRect logicalLeftSelectionGap(RenderBlock* rootBlock, const LayoutPoint& rootBlockPhysicalPosition, const LayoutSize& offsetFromRootBlock,
                                        RenderObject* selObj, LayoutUnit logicalLeft, LayoutUnit logicalTop, LayoutUnit logicalHeight, const PaintInfo*);