[CSS Grid Layout] Handle percentages of indefinite sizes in minmax()

Source/core/rendering/style/GridLength.h

 /*
  * Copyright (C) 2013 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 42 matching lines @@
     {
     }
 
     bool isLength() const { return m_type == LengthType; }
     bool isFlex() const { return m_type == FlexType; }
 
     const Length& length() const { ASSERT(isLength()); return m_length; }
 
     double flex() const { ASSERT(isFlex()); return m_flex; }
 
+    bool isPercentage() const { return m_type == LengthType && m_length.isPercent(); }
+
     bool operator==(const GridLength& o) const
     {
         return m_length == o.m_length && m_flex == o.m_flex && m_type == o.m_type;
     }
 
     bool isContentSized() const { return m_type == LengthType && (m_length.isAuto() || m_length.isMinContent() || m_length.isMaxContent()); }
 
 private:
     // Ideally we would put the 2 following fields in a union, but Length has a constructor,
     // a destructor and a copy assignment which isn't allowed.
     Length m_length;
     double m_flex;
     enum GridLengthType {
         LengthType,
         FlexType
     };
     GridLengthType m_type;
 };
 
 } // namespace blink
 
 #endif // GridLength_h