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

Source/core/rendering/RenderFlexibleBox.cpp

Index: Source/core/rendering/RenderFlexibleBox.cpp
diff --git a/Source/core/rendering/RenderFlexibleBox.cpp b/Source/core/rendering/RenderFlexibleBox.cpp
index a31244c74f35188eb60bb4ddbc6de4b13e595519..52772a52e7f09fa9a6111ed36de994ea7d5f5e0a 100644
--- a/Source/core/rendering/RenderFlexibleBox.cpp
+++ b/Source/core/rendering/RenderFlexibleBox.cpp
@@ -243,10 +243,7 @@ void RenderFlexibleBox::layoutBlock(bool relayoutChildren)
 
     LayoutStateMaintainer statePusher(view(), this, locationOffset(), hasTransform() || hasReflection() || style()->isFlippedBlocksWritingMode());
 
-    // Regions changing widths can force us to relayout our children.
     RenderFlowThread* flowThread = flowThreadContainingBlock();
-    if (logicalWidthChangedInRegions(flowThread))
-        relayoutChildren = true;
     if (updateRegionsAndShapesLogicalSize(flowThread))
         relayoutChildren = true;
 
@@ -447,9 +444,7 @@ LayoutUnit RenderFlexibleBox::computeMainAxisExtentForChild(RenderBox* child, Si
             child->layoutIfNeeded();
         return child->computeContentLogicalHeight(size, child->logicalHeight() - child->borderAndPaddingLogicalHeight());
     }
-    // FIXME: Figure out how this should work for regions and pass in the appropriate values.
-    RenderRegion* region = 0;
-    return child->computeLogicalWidthInRegionUsing(sizeType, size, contentLogicalWidth(), this, region) - child->borderAndPaddingLogicalWidth();
+    return child->computeLogicalWidthUsing(sizeType, size, contentLogicalWidth(), this) - child->borderAndPaddingLogicalWidth();
 }
 
 WritingMode RenderFlexibleBox::transformedWritingMode() const
@@ -1029,7 +1024,7 @@ void RenderFlexibleBox::prepareChildForPositionedLayout(RenderBox* child, Layout
     LayoutUnit inlinePosition = isColumnFlow() ? crossAxisOffset : mainAxisOffset;
     if (layoutMode == FlipForRowReverse && style()->flexDirection() == FlowRowReverse)
         inlinePosition = mainAxisExtent() - mainAxisOffset;
-    childLayer->setStaticInlinePosition(inlinePosition); // FIXME: Not right for regions.
+    childLayer->setStaticInlinePosition(inlinePosition);
 
     LayoutUnit staticBlockPosition = isColumnFlow() ? mainAxisOffset : crossAxisOffset;
     if (childLayer->staticBlockPosition() != staticBlockPosition) {
@@ -1371,7 +1366,7 @@ void RenderFlexibleBox::applyStretchAlignmentToChild(RenderBox* child, LayoutUni
         // FIXME: If the child doesn't have orthogonal flow, then it already has an override width set, so use it.
         if (hasOrthogonalFlow(child)) {
             LayoutUnit childWidth = std::max<LayoutUnit>(0, lineCrossAxisExtent - crossAxisMarginExtentForChild(child));
-            childWidth = child->constrainLogicalWidthInRegionByMinMax(childWidth, childWidth, this);
+            childWidth = child->constrainLogicalWidthByMinMax(childWidth, childWidth, this);
 
             if (childWidth != child->logicalWidth()) {
                 child->setOverrideLogicalContentWidth(childWidth - child->borderAndPaddingLogicalWidth());