Implement CSSPaintValue and add a layout test.

third_party/WebKit/Source/modules/csspaint/CSSPaintImageGeneratorImpl.cpp

Index: third_party/WebKit/Source/modules/csspaint/CSSPaintImageGeneratorImpl.cpp
diff --git a/third_party/WebKit/Source/modules/csspaint/CSSPaintImageGeneratorImpl.cpp b/third_party/WebKit/Source/modules/csspaint/CSSPaintImageGeneratorImpl.cpp
index 6b488a17c85bf29c77c269dc39b9e4d85af0e686..98f41edc633e3726f587200e253b257e781597fc 100644
--- a/third_party/WebKit/Source/modules/csspaint/CSSPaintImageGeneratorImpl.cpp
+++ b/third_party/WebKit/Source/modules/csspaint/CSSPaintImageGeneratorImpl.cpp
@@ -4,6 +4,7 @@
 
 #include "modules/csspaint/CSSPaintImageGeneratorImpl.h"
 
+#include "core/css/CSSVariableData.h"
 #include "core/dom/Document.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "modules/csspaint/CSSPaintDefinition.h"
@@ -52,8 +53,10 @@ void CSSPaintImageGeneratorImpl::setDefinition(CSSPaintDefinition* definition) {
 PassRefPtr<Image> CSSPaintImageGeneratorImpl::paint(
     const LayoutObject& layoutObject,
     const IntSize& size,
-    float zoom) {
-  return m_definition ? m_definition->paint(layoutObject, size, zoom) : nullptr;
+    float zoom,
+    const Vector<RefPtr<CSSVariableData>>& data) {
+  return m_definition ? m_definition->paint(layoutObject, size, zoom, data)
+                      : nullptr;
 }
 
 const Vector<CSSPropertyID>&