Fix incorrect assumption about children's flexBasis

Source/core/rendering/RenderFlexibleBox.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 593 matching lines @@
 {
     child.clearOverrideSize();
 
     if (child.style()->hasAspectRatio() || child.isImage() || child.isVideo() || child.isCanvas())
         UseCounter::count(document(), UseCounter::AspectRatioFlexItem);
 
     Length flexBasis = flexBasisForChild(child);
     if (preferredMainAxisExtentDependsOnLayout(flexBasis, hasInfiniteLineLength)) {
         LayoutUnit mainAxisExtent;
         if (hasOrthogonalFlow(child)) {
-            if (child.needsLayout() || relayoutChildren) {
+            if (child.needsLayout() || relayoutChildren || !m_intrinsicSizeAlongMainAxis.contains(&child)) {
                 m_intrinsicSizeAlongMainAxis.remove(&child);
                 child.forceChildLayout();
                 m_intrinsicSizeAlongMainAxis.set(&child, child.logicalHeight());
             }
-            ASSERT(m_intrinsicSizeAlongMainAxis.contains(&child));
             mainAxisExtent = m_intrinsicSizeAlongMainAxis.get(&child);
         } else {
             mainAxisExtent = child.maxPreferredLogicalWidth();
         }
         ASSERT(mainAxisExtent - mainAxisBorderAndPaddingExtentForChild(child) >= 0);
         return mainAxisExtent - mainAxisBorderAndPaddingExtentForChild(child);
     }
     return std::max(LayoutUnit(0), computeMainAxisExtentForChild(child, MainOrPreferredSize, flexBasis));
 }
 
@@ skipping 764 matching lines @@
             ASSERT(child);
             LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
             LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
             LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
             adjustAlignmentForChild(*child, newOffset - originalOffset);
         }
     }
 }
 
 }