Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

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 d26fb66b83a26164a161711f8db6ed95e4d11c5c..7a12db5420cceb7eca1d5c6ce0228ece96f526f7 100644
--- a/Source/core/rendering/style/RenderStyle.h
+++ b/Source/core/rendering/style/RenderStyle.h
@@ -853,9 +853,6 @@ public:
     EPageBreak columnBreakBefore() const { return static_cast<EPageBreak>(rareNonInheritedData->m_multiCol->m_breakBefore); }
     EPageBreak columnBreakInside() const { return static_cast<EPageBreak>(rareNonInheritedData->m_multiCol->m_breakInside); }
     EPageBreak columnBreakAfter() const { return static_cast<EPageBreak>(rareNonInheritedData->m_multiCol->m_breakAfter); }
-    EPageBreak regionBreakBefore() const { return static_cast<EPageBreak>(rareNonInheritedData->m_regionBreakBefore); }
-    EPageBreak regionBreakInside() const { return static_cast<EPageBreak>(rareNonInheritedData->m_regionBreakInside); }
-    EPageBreak regionBreakAfter() const { return static_cast<EPageBreak>(rareNonInheritedData->m_regionBreakAfter); }
     const TransformOperations& transform() const { return rareNonInheritedData->m_transform->m_operations; }
     Length transformOriginX() const { return rareNonInheritedData->m_transform->m_x; }
     Length transformOriginY() const { return rareNonInheritedData->m_transform->m_y; }
@@ -893,11 +890,6 @@ public:
 
     // End CSS3 Getters
 
-    const AtomicString& flowThread() const { return rareNonInheritedData->m_flowThread; }
-    bool hasFlowFrom() const { return !rareNonInheritedData->m_regionThread.isNull(); }
-    const AtomicString& regionThread() const { return rareNonInheritedData->m_regionThread; }
-    RegionFragment regionFragment() const { return static_cast<RegionFragment>(rareNonInheritedData->m_regionFragment); }
-
     const AtomicString& lineGrid() const { return rareInheritedData->m_lineGrid; }
     LineSnap lineSnap() const { return static_cast<LineSnap>(rareInheritedData->m_lineSnap); }
     LineAlign lineAlign() const { return static_cast<LineAlign>(rareInheritedData->m_lineAlign); }
@@ -1322,9 +1314,6 @@ public:
     // For valid values of column-break-inside see http://www.w3.org/TR/css3-multicol/#break-before-break-after-break-inside
     void setColumnBreakInside(EPageBreak p) { ASSERT(p == PBAUTO || p == PBAVOID); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_breakInside, p); }
     void setColumnBreakAfter(EPageBreak p) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_breakAfter, p); }
-    void setRegionBreakBefore(EPageBreak p) { SET_VAR(rareNonInheritedData, m_regionBreakBefore, p); }
-    void setRegionBreakInside(EPageBreak p) { ASSERT(p == PBAUTO || p == PBAVOID); SET_VAR(rareNonInheritedData, m_regionBreakInside, p); }
-    void setRegionBreakAfter(EPageBreak p) { SET_VAR(rareNonInheritedData, m_regionBreakAfter, p); }
     void inheritColumnPropertiesFrom(RenderStyle* parent) { rareNonInheritedData.access()->m_multiCol = parent->rareNonInheritedData->m_multiCol; }
     void setTransform(const TransformOperations& ops) { SET_VAR(rareNonInheritedData.access()->m_transform, m_operations, ops); }
     void setTransformOriginX(Length l) { SET_VAR(rareNonInheritedData.access()->m_transform, m_x, l); }
@@ -1355,10 +1344,6 @@ public:
     void setLineSnap(LineSnap lineSnap) { SET_VAR(rareInheritedData, m_lineSnap, lineSnap); }
     void setLineAlign(LineAlign lineAlign) { SET_VAR(rareInheritedData, m_lineAlign, lineAlign); }
 
-    void setFlowThread(const AtomicString& flowThread) { SET_VAR(rareNonInheritedData, m_flowThread, flowThread); }
-    void setRegionThread(const AtomicString& regionThread) { SET_VAR(rareNonInheritedData, m_regionThread, regionThread); }
-    void setRegionFragment(RegionFragment regionFragment) { SET_VAR(rareNonInheritedData, m_regionFragment, regionFragment); }
-
     void setWrapFlow(WrapFlow wrapFlow) { SET_VAR(rareNonInheritedData, m_wrapFlow, wrapFlow); }
     void setWrapThrough(WrapThrough wrapThrough) { SET_VAR(rareNonInheritedData, m_wrapThrough, wrapThrough); }
 
@@ -1513,12 +1498,6 @@ public:
     bool isDisplayReplacedType() const { return isDisplayReplacedType(display()); }
     bool isDisplayInlineType() const { return isDisplayInlineType(display()); }
     bool isOriginalDisplayInlineType() const { return isDisplayInlineType(originalDisplay()); }
-    bool isDisplayRegionType() const
-    {
-        return display() == BLOCK || display() == INLINE_BLOCK
-            || display() == TABLE_CELL || display() == TABLE_CAPTION
-            || display() == LIST_ITEM;
-    }
 
     bool setWritingMode(WritingMode v)
     {
@@ -1727,10 +1706,6 @@ public:
     static LineSnap initialLineSnap() { return LineSnapNone; }
     static LineAlign initialLineAlign() { return LineAlignNone; }
 
-    static const AtomicString& initialFlowThread() { return nullAtom; }
-    static const AtomicString& initialRegionThread() { return nullAtom; }
-    static RegionFragment initialRegionFragment() { return AutoRegionFragment; }
-
     static WrapFlow initialWrapFlow() { return WrapFlowAuto; }
     static WrapThrough initialWrapThrough() { return WrapThroughWrap; }