Do not calculate the same gradient length for every color stops.

Source/core/css/CSSGradientValue.cpp

Index: Source/core/css/CSSGradientValue.cpp
diff --git a/Source/core/css/CSSGradientValue.cpp b/Source/core/css/CSSGradientValue.cpp
index 1b048ece7a40da7a84ca5a1f9ac8af8b4cc35168..d9a3ea24aac1cc9fa9d6bfc16ca683f20705bb77 100644
--- a/Source/core/css/CSSGradientValue.cpp
+++ b/Source/core/css/CSSGradientValue.cpp
@@ -258,6 +258,7 @@ void CSSGradientValue::addStops(Gradient* gradient, const CSSToLengthConversionD
                 if (!computedGradientLength) {
                     FloatSize gradientSize(gradientStart - gradientEnd);
                     gradientLength = gradientSize.diagonalLength();
+                    computedGradientLength = true;
                 }
                 float length;
                 if (stop.m_position->isLength())
@@ -353,6 +354,7 @@ void CSSGradientValue::addStops(Gradient* gradient, const CSSToLengthConversionD
                 if (!computedGradientLength) {
                     FloatSize gradientSize(gradientStart - gradientEnd);
                     gradientLength = gradientSize.diagonalLength();
+                    computedGradientLength = true;
                 }
 
                 if (maxLengthForRepeat > gradientLength)