*** DO NOT LAND *** Attempt to understand Regions complexity

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 53ca757e7d8614505f11fa057fb4c8f2e7f608ae..228438d9b5b14efd9f1bc2ad402a0a9560f63bf9 100644
--- a/Source/core/rendering/RenderBlock.h
+++ b/Source/core/rendering/RenderBlock.h
@@ -247,39 +247,9 @@ public:
 
     virtual void scrollbarsChanged(bool /*horizontalScrollbarChanged*/, bool /*verticalScrollbarChanged*/) { };
 
-    LayoutUnit logicalLeftOffsetForContent(RenderRegion*) const;
-    LayoutUnit logicalRightOffsetForContent(RenderRegion*) const;
-    LayoutUnit availableLogicalWidthForContent(RenderRegion* region) const
+    LayoutUnit availableLogicalWidthForContent() const
     {
-        return max<LayoutUnit>(0, logicalRightOffsetForContent(region) - logicalLeftOffsetForContent(region));
-    }
-    LayoutUnit startOffsetForContent(RenderRegion* region) const
-    {
-        return style()->isLeftToRightDirection() ? logicalLeftOffsetForContent(region) : logicalWidth() - logicalRightOffsetForContent(region);
-    }
-    LayoutUnit endOffsetForContent(RenderRegion* region) const
-    {
-        return !style()->isLeftToRightDirection() ? logicalLeftOffsetForContent(region) : logicalWidth() - logicalRightOffsetForContent(region);
-    }
-    LayoutUnit logicalLeftOffsetForContent(LayoutUnit blockOffset) const
-    {
-        return logicalLeftOffsetForContent(regionAtBlockOffset(blockOffset));
-    }
-    LayoutUnit logicalRightOffsetForContent(LayoutUnit blockOffset) const
-    {
-        return logicalRightOffsetForContent(regionAtBlockOffset(blockOffset));
-    }
-    LayoutUnit availableLogicalWidthForContent(LayoutUnit blockOffset) const
-    {
-        return availableLogicalWidthForContent(regionAtBlockOffset(blockOffset));
-    }
-    LayoutUnit startOffsetForContent(LayoutUnit blockOffset) const
-    {
-        return startOffsetForContent(regionAtBlockOffset(blockOffset));
-    }
-    LayoutUnit endOffsetForContent(LayoutUnit blockOffset) const
-    {
-        return endOffsetForContent(regionAtBlockOffset(blockOffset));
+        return max<LayoutUnit>(0, logicalRightOffsetForContent() - logicalLeftOffsetForContent());
     }
     LayoutUnit logicalLeftOffsetForContent() const { return isHorizontalWritingMode() ? borderLeft() + paddingLeft() : borderTop() + paddingTop(); }
     LayoutUnit logicalRightOffsetForContent() const { return logicalLeftOffsetForContent() + availableLogicalWidth(); }
@@ -385,9 +355,6 @@ protected:
 
     virtual void computeSelfHitTestRects(Vector<LayoutRect>&, const LayoutPoint& layerOffset) const OVERRIDE;
 
-    bool updateRegionsAndShapesLogicalSize(RenderFlowThread*);
-    void computeRegionRangeForBlock(RenderFlowThread*);
-
     void updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, RenderBox*);
 
     virtual void checkForPaginationLogicalHeightChange(LayoutUnit& pageLogicalHeight, bool& pageLogicalHeightChanged, bool& hasSpecifiedPageLogicalHeight);
@@ -396,7 +363,6 @@ protected:
 
 private:
     void computeShapeSize();
-    void updateRegionsAndShapesAfterChildLayout(RenderFlowThread*, bool);
     void updateShapeInsideInfoAfterStyleChange(const ShapeValue*, const ShapeValue* oldShape);
     void relayoutShapeDescendantIfMoved(RenderBlock* child, LayoutSize offset);
 
@@ -555,8 +521,7 @@ protected:
     void updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight);
 
     LayoutUnit adjustForUnsplittableChild(RenderBox* child, LayoutUnit logicalOffset, bool includeMargins = false); // If the child is unsplittable and can't fit on the current page, return the top of the next page/column.
-    void adjustLinePositionForPagination(RootInlineBox*, LayoutUnit& deltaOffset, RenderFlowThread*); // Computes a deltaOffset value that put a line at the top of the next page if it doesn't fit on the current page.
-    void updateRegionForLine(RootInlineBox*) const;
+    void adjustLinePositionForPagination(RootInlineBox*, LayoutUnit& deltaOffset); // Computes a deltaOffset value that put a line at the top of the next page if it doesn't fit on the current page.
 
     // Adjust from painting offsets to the local coords of this renderer
     void offsetForContents(LayoutPoint&) const;
@@ -564,9 +529,7 @@ protected:
     // This function is called to test a line box that has moved in the block direction to see if it has ended up in a new
     // region/page/column that has a different available line width than the old one. Used to know when you have to dirty a
     // line, i.e., that it can't be re-used.
-    bool lineWidthForPaginatedLineChanged(RootInlineBox*, LayoutUnit lineDelta, RenderFlowThread*) const;
-
-    bool logicalWidthChangedInRegions(RenderFlowThread*) const;
+    bool lineWidthForPaginatedLineChanged(RootInlineBox*, LayoutUnit lineDelta) const;
 
     virtual bool requiresColumns(int desiredColumnCount) const;
 
@@ -576,8 +539,6 @@ protected:
 
 public:
     virtual LayoutUnit offsetFromLogicalTopOfFirstPage() const OVERRIDE FINAL;
-    RenderRegion* regionAtBlockOffset(LayoutUnit) const;
-    RenderRegion* clampToStartAndEndRegions(RenderRegion*) const;
 
 public:
 
@@ -631,7 +592,7 @@ inline bool RenderBlock::allowsShapeInsideInfoSharing(const RenderBlock* other)
 {
     if (!other)
         return false;
-    for (const RenderBlock* current = this; current && current != other && !current->isRenderFlowThread(); current = current->containingBlock()) {
+    for (const RenderBlock* current = this; current && current != other; current = current->containingBlock()) {
         if (current->isInline() || current->isFloating())
             return false;
         if (current->parent() != current->containingBlock())