Merge 123062 - Crash in RenderTableSection::addCell.

Source/WebCore/rendering/RenderBox.cpp

Index: Source/WebCore/rendering/RenderBox.cpp
===================================================================
--- Source/WebCore/rendering/RenderBox.cpp	(revision 123512)
+++ Source/WebCore/rendering/RenderBox.cpp	(working copy)
@@ -3951,9 +3951,11 @@
 {
     // FIXME: The table code should handle that automatically. If not,
     // we should fix it and remove the table part checks.
-    if (box->isTable())
-        toRenderTable(box)->setNeedsSectionRecalc();
-    else if (box->isTableSection())
+    if (box->isTable()) {
+        // Because we may have added some sections with already computed column structures, we need to
+        // sync the table structure with them now. This avoids crashes when adding new cells to the table.
+        toRenderTable(box)->forceSectionsRecalc();
+    } else if (box->isTableSection())
         toRenderTableSection(box)->setNeedsCellRecalc();
 
     box->setNeedsLayoutAndPrefWidthsRecalc();