Add "alpha" option to PaintWorklet

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

 // 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.
 
 #include "modules/csspaint/CSSPaintImageGeneratorImpl.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "modules/csspaint/CSSPaintDefinition.h"
 #include "modules/csspaint/PaintWorklet.h"
@@ skipping 52 matching lines @@
     DEFINE_STATIC_LOCAL(Vector<CSSPropertyID>, emptyVector, ());
     return m_definition ? m_definition->nativeInvalidationProperties() : emptyVector;
 }
 
 const Vector<AtomicString>& CSSPaintImageGeneratorImpl::customInvalidationProperties() const
 {
     DEFINE_STATIC_LOCAL(Vector<AtomicString>, emptyVector, ());
     return m_definition ? m_definition->customInvalidationProperties() : emptyVector;
 }
 
+bool CSSPaintImageGeneratorImpl::hasAlpha() const
+{
+    return m_definition && m_definition->hasAlpha();
+}
+
 DEFINE_TRACE(CSSPaintImageGeneratorImpl)
 {
     visitor->trace(m_definition);
     visitor->trace(m_observer);
     CSSPaintImageGenerator::trace(visitor);
 }
 
 } // namespace blink