[This bug mirrors https://code.google.com/p/chromium/issues/detail?id=269320] There is no equivalent CSSCalcExpressionNode in the CSS layer to CalcExpressionBlendLength (define in (platform/CalculationValue.h)). Currently an equivalent *expression tree* can be created to represent the blend, but this requires 3 BinaryExpressionNodes: ((1 - progress) * start) + (progress * end)
I don't think we want this anymore, it doesn't seem useful.