Make currentColor keyword in linear-gradient work

Source/core/css/CSSGradientValue.h

Index: Source/core/css/CSSGradientValue.h
diff --git a/Source/core/css/CSSGradientValue.h b/Source/core/css/CSSGradientValue.h
index 4a5f7c0ac252a57800ac5994da25933c029b22b8..2a6690b03d312f2aeb29cae52b680e167a281d10 100644
--- a/Source/core/css/CSSGradientValue.h
+++ b/Source/core/css/CSSGradientValue.h
@@ -135,7 +135,7 @@ protected:
     {
     }
 
-    void addStops(Gradient*, const CSSToLengthConversionData&, float maxLengthForRepeat = 0);
+    void addStops(Gradient*, const CSSToLengthConversionData&, float maxLengthForRepeat, const RenderObject&);
 
     // Resolve points/radii to front end values.
     FloatPoint computeEndPoint(CSSPrimitiveValue*, CSSPrimitiveValue*, const CSSToLengthConversionData&, const IntSize&);
@@ -171,7 +171,7 @@ public:
     String customCSSText() const;
 
     // Create the gradient for a given size.
-    PassRefPtr<Gradient> createGradient(const CSSToLengthConversionData&, const IntSize&);
+    PassRefPtr<Gradient> createGradient(const CSSToLengthConversionData&, const IntSize&, const RenderObject&);
 
     PassRefPtrWillBeRawPtr<CSSLinearGradientValue> clone() const
     {
@@ -223,7 +223,7 @@ public:
     void setEndVerticalSize(PassRefPtrWillBeRawPtr<CSSPrimitiveValue> val) { m_endVerticalSize = val; }
 
     // Create the gradient for a given size.
-    PassRefPtr<Gradient> createGradient(const CSSToLengthConversionData&, const IntSize&);
+    PassRefPtr<Gradient> createGradient(const CSSToLengthConversionData&, const IntSize&, const RenderObject&);
 
     bool equals(const CSSRadialGradientValue&) const;