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

Source/core/css/CSSGradientValue.cpp

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 240 matching lines @@
         else
             stops[i].color = resolveStopColor(stop.m_color.get(), object);
 
         if (stop.m_position) {
             if (stop.m_position->isPercentage())
                 stops[i].offset = stop.m_position->getFloatValue(CSSPrimitiveValue::CSS_PERCENTAGE) / 100;
             else if (stop.m_position->isLength() || stop.m_position->isCalculatedPercentageWithLength()) {
                 if (!computedGradientLength) {
                     FloatSize gradientSize(gradientStart - gradientEnd);
                     gradientLength = gradientSize.diagonalLength();
+                    computedGradientLength = true;
                 }
                 float length;
                 if (stop.m_position->isLength())
                     length = stop.m_position->computeLength<float>(conversionData);
                 else
                     length = stop.m_position->cssCalcValue()->toCalcValue(conversionData)->evaluate(gradientLength);
                 stops[i].offset = (gradientLength > 0) ? length / gradientLength : 0;
             } else {
                 ASSERT_NOT_REACHED();
                 stops[i].offset = 0;
@@ skipping 75 matching lines @@
             stops.shrink(1);
         } else {
             float maxExtent = 1;
 
             // Radial gradients may need to extend further than the endpoints, because they have
             // to repeat out to the corners of the box.
             if (isRadialGradientValue()) {
                 if (!computedGradientLength) {
                     FloatSize gradientSize(gradientStart - gradientEnd);
                     gradientLength = gradientSize.diagonalLength();
+                    computedGradientLength = true;
                 }
 
                 if (maxLengthForRepeat > gradientLength)
                     maxExtent = gradientLength > 0 ? maxLengthForRepeat / gradientLength : 0;
             }
 
             size_t originalNumStops = numStops;
             size_t originalFirstStopIndex = 0;
 
             // Work backwards from the first, adding stops until we get one before 0.
@@ skipping 914 matching lines @@
     visitor->trace(m_firstRadius);
     visitor->trace(m_secondRadius);
     visitor->trace(m_shape);
     visitor->trace(m_sizingBehavior);
     visitor->trace(m_endHorizontalSize);
     visitor->trace(m_endVerticalSize);
     CSSGradientValue::traceAfterDispatch(visitor);
 }
 
 } // namespace blink