Add "alpha" option to PaintWorklet

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 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&) 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