Move isValid/isCurrentColor from Color to StyleColor

Source/core/rendering/RenderTableCell.cpp

Index: Source/core/rendering/RenderTableCell.cpp
diff --git a/Source/core/rendering/RenderTableCell.cpp b/Source/core/rendering/RenderTableCell.cpp
index f13dc0a006a71fe4979afa7932442d3087b6cba7..429d5219ecf9b73de0ec62e10610c23e57cc0cd9 100644
--- a/Source/core/rendering/RenderTableCell.cpp
+++ b/Source/core/rendering/RenderTableCell.cpp
@@ -1168,7 +1168,7 @@ void RenderTableCell::paintBackgroundsBehindCell(PaintInfo& paintInfo, const Lay
     if (backgroundObject != this)
         adjustedPaintOffset.moveBy(location());
 
-    Color c = backgroundObject->resolveColor(CSSPropertyBackgroundColor);
+    StyleColor c = backgroundObject->resolveStyleColor(CSSPropertyBackgroundColor);
     const FillLayer* bgLayer = backgroundObject->style()->backgroundLayers();
 
     if (bgLayer->hasImage() || c.isValid()) {
@@ -1181,7 +1181,7 @@ void RenderTableCell::paintBackgroundsBehindCell(PaintInfo& paintInfo, const Lay
                 width() - borderLeft() - borderRight(), height() - borderTop() - borderBottom());
             paintInfo.context->clip(clipRect);
         }
-        paintFillLayers(paintInfo, c, bgLayer, LayoutRect(adjustedPaintOffset, pixelSnappedSize()), BackgroundBleedNone, CompositeSourceOver, backgroundObject);
+        paintFillLayers(paintInfo, c.color(), bgLayer, LayoutRect(adjustedPaintOffset, pixelSnappedSize()), BackgroundBleedNone, CompositeSourceOver, backgroundObject);
     }
 }