Implement color stop position syntax from CSS Image Values 4

third_party/WebKit/Source/core/css/CSSGradientValue.cpp

 /*
  * Copyright (C) 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2015 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:
  * 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
@@ skipping 1056 matching lines @@
 }
 
 DEFINE_TRACE_AFTER_DISPATCH(CSSLinearGradientValue) {
   visitor->trace(m_angle);
   CSSGradientValue::traceAfterDispatch(visitor);
 }
 
 void CSSGradientValue::appendCSSTextForColorStops(
     StringBuilder& result,
     bool requiresSeparator) const {
+  const CSSValue* prevColor = nullptr;
+
   for (const auto& stop : m_stops) {
+    bool isColorRepeat = false;
+    if (RuntimeEnabledFeatures::multipleColorStopPositionsEnabled()) {
+      isColorRepeat = stop.m_color && stop.m_offset &&
+                      dataEquivalent(stop.m_color.get(), prevColor);
+    }
+
     if (requiresSeparator) {
-      result.append(", ");
+      if (!isColorRepeat)
+        result.append(", ");
     } else {
       requiresSeparator = true;
     }
 
-    if (stop.m_color)
+    if (stop.m_color && !isColorRepeat)
       result.append(stop.m_color->cssText());
     if (stop.m_color && stop.m_offset)
       result.append(' ');
     if (stop.m_offset)
       result.append(stop.m_offset->cssText());
+
+    // Reset prevColor if we've emitted a color repeat.
+    prevColor = isColorRepeat ? nullptr : stop.m_color.get();
   }
 }
 
 void CSSGradientValue::appendCSSTextForDeprecatedColorStops(
     StringBuilder& result) const {
   for (unsigned i = 0; i < m_stops.size(); i++) {
     const CSSGradientColorStop& stop = m_stops[i];
     result.append(", ");
     if (stop.m_offset->getDoubleValue() == 0) {
       result.append("from(");
@@ skipping 408 matching lines @@
          dataEquivalent(m_fromAngle, other.m_fromAngle) &&
          m_stops == other.m_stops;
 }
 
 DEFINE_TRACE_AFTER_DISPATCH(CSSConicGradientValue) {
   visitor->trace(m_fromAngle);
   CSSGradientValue::traceAfterDispatch(visitor);
 }
 
 }  // namespace blink