Improve multicol preferred/intrinsic width calculation.

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index e0d02f6d870ea9ff9a3ad3318a8ab27db2b15446..967e669c5fa58f34e4c80478d56fecf99ead6c5c 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -5711,6 +5711,8 @@ void RenderBlock::computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, Lay
 
     maxLogicalWidth = max(minLogicalWidth, maxLogicalWidth);
 
+    adjustIntrinsicLogicalWidthsForColumns(minLogicalWidth, maxLogicalWidth);
+
     // A horizontal marquee with inline children has no minimum width.
     if (childrenInline() && isMarquee() && toRenderMarquee(this)->isHorizontal())
         minLogicalWidth = 0;
@@ -5767,6 +5769,33 @@ void RenderBlock::computePreferredLogicalWidths()
     clearPreferredLogicalWidthsDirty();
 }
 
+void RenderBlock::adjustIntrinsicLogicalWidthsForColumns(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
+{
+    // FIXME: make this method virtual and move the code to RenderMultiColumnBlock once the old
+    // multicol code is gone.
+
+    if (!style()->hasAutoColumnCount() || !style()->hasAutoColumnWidth()) {
+        // The min/max intrinsic widths calculated really tell how much space elements need when
+        // laid out inside the columns. In order to eventually end up with the desired column width,
+        // we need to convert them to values pertaining to the multicol container.
+        int columnCount = style()->hasAutoColumnCount() ? 1 : style()->columnCount();
+        LayoutUnit columnWidth;
+        LayoutUnit gapExtra = (columnCount - 1) * columnGap();
+        if (style()->hasAutoColumnWidth()) {
+            minLogicalWidth = minLogicalWidth * columnCount + gapExtra;
+        } else {
+            columnWidth = style()->columnWidth();
+            minLogicalWidth = min(minLogicalWidth, columnWidth);
+        }
+        // FIXME: If column-count is auto here, we should resolve it to calculate the maximum
+        // intrinsic width, instead of pretending that it's 1. The only way to do that is by
+        // performing a layout pass, but this is not an appropriate time or place for layout. The
+        // good news is that if height is unconstrained and there are no explicit breaks, the
+        // resolved column-count really should be 1.
+        maxLogicalWidth = max(maxLogicalWidth, columnWidth) * columnCount + gapExtra;
+    }
+}
+
 struct InlineMinMaxIterator {
 /* InlineMinMaxIterator is a class that will iterate over all render objects that contribute to
    inline min/max width calculations.  Note the following about the way it walks: