[CSS Grid Layout] Flex factor sum must be 1 at least.

Source/core/layout/LayoutGrid.cpp

Index: Source/core/layout/LayoutGrid.cpp
diff --git a/Source/core/layout/LayoutGrid.cpp b/Source/core/layout/LayoutGrid.cpp
index fa0f179b1a0fff95e96561186f81dfd73a1ad9b9..7546f750de5e76f39886342b6b75ba8f9f3bb1ee 100644
--- a/Source/core/layout/LayoutGrid.cpp
+++ b/Source/core/layout/LayoutGrid.cpp
@@ -575,6 +575,11 @@ double LayoutGrid::computeNormalizedFractionBreadth(Vector<GridTrack>& tracks, c
         availableLogicalSpaceIgnoringFractionTracks += track.m_track->baseSize();
     }
 
+    // Let flex factor sum be the sum of the flex factors of the flexible tracks. If this value
+    // is less than 1, set it to 1 instead.
+    if (accumulatedFractions < 1)
+        return availableLogicalSpaceIgnoringFractionTracks;
+
     return availableLogicalSpaceIgnoringFractionTracks / accumulatedFractions;
 }