Implement CSSPaintValue and add a layout test.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CSSPaintImageGeneratorImpl_h
 #define CSSPaintImageGeneratorImpl_h
 
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "core/css/CSSPaintImageGenerator.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/heap/Handle.h"
 #include <v8.h>
 
 namespace blink {
 
 class CSSPaintDefinition;
+class CSSVariableData;
 class Document;
 class Image;
 
 class CSSPaintImageGeneratorImpl final : public CSSPaintImageGenerator {
  public:
   static CSSPaintImageGenerator* create(const String& name,
                                         Document&,
                                         Observer*);
   ~CSSPaintImageGeneratorImpl() override;
 
   PassRefPtr<Image> paint(const LayoutObject&,
                           const IntSize&,
-                          float zoom) final;
+                          float zoom,
+                          const Vector<RefPtr<CSSVariableData>>&) final;
   const Vector<CSSPropertyID>& nativeInvalidationProperties() const final;
   const Vector<AtomicString>& customInvalidationProperties() const final;
   bool hasAlpha() const final;
 
   // Should be called from the PaintWorkletGlobalScope when a javascript class
   // is registered with the same name.
   void setDefinition(CSSPaintDefinition*);
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   CSSPaintImageGeneratorImpl(Observer*);
   CSSPaintImageGeneratorImpl(CSSPaintDefinition*);
 
   Member<CSSPaintDefinition> m_definition;
   Member<Observer> m_observer;
 };
 
 }  // namespace blink
 
 #endif  // CSSPaintImageGeneratorImpl_h