Add "alpha" option to PaintWorklet

third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.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 PaintRenderingContext2D_h
 #define PaintRenderingContext2D_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "modules/ModulesExport.h"
 #include "modules/canvas2d/BaseRenderingContext2D.h"
 #include "platform/graphics/ImageBuffer.h"
 #include <memory>
 
 class SkCanvas;
 
 namespace blink {
 
 class CanvasImageSource;
 class Color;
 
 class MODULES_EXPORT PaintRenderingContext2D : public BaseRenderingContext2D, public GarbageCollectedFinalized<PaintRenderingContext2D>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
     USING_GARBAGE_COLLECTED_MIXIN(PaintRenderingContext2D);
     WTF_MAKE_NONCOPYABLE(PaintRenderingContext2D);
 public:
-    static PaintRenderingContext2D* create(std::unique_ptr<ImageBuffer> imageBuffer)
+    static PaintRenderingContext2D* create(std::unique_ptr<ImageBuffer> imageBuffer, bool hasAlphaChannel)
     {
-        return new PaintRenderingContext2D(std::move(imageBuffer));
+        return new PaintRenderingContext2D(std::move(imageBuffer), hasAlphaChannel);
     }
 
     // BaseRenderingContext2D
 
     // PaintRenderingContext2D doesn't have any pixel readback so the origin
     // is always clean, and unable to taint it.
     bool originClean() const final { return true; }
     void setOriginTainted() final { }
     bool wouldTaintOrigin(CanvasImageSource*, ExecutionContext*) final { return false; }
 
@@ skipping 16 matching lines @@
     // TODO(ikilpatrick): We'll need to either only accept resolved filters
     // from a typed-om <filter> object, or use the appropriate style resolution
     // host to determine 'em' units etc in filters. At the moment just pretend
     // that we don't have a filter set.
     bool stateHasFilter() final { return false; }
     SkImageFilter* stateGetFilter() final { return nullptr; }
     void snapshotStateForFilter() final { }
 
     void validateStateStack() final;
 
-    bool hasAlpha() const final { return true; }
+    bool hasAlpha() const final { return m_hasAlphaChannel; }

[ikilpatrick, 2016/06/22 16:00:24]

we can probably remove this virtual method now.

This was initially introduced in BaseRC2D as PaintRC2D had different behaviour
from CanvasRC2D.

Can just pass hasAlpha to BaseRC2D now.

[Gleb Lanbin, 2016/06/22 21:23:45]

hasAlpha is declared as a pure virtual method in BaseRC2D so it must be
overridden.

 
     // PaintRenderingContext2D cannot lose it's context.
     bool isContextLost() const final { return false; }
 
 private:
-    explicit PaintRenderingContext2D(std::unique_ptr<ImageBuffer>);
+    PaintRenderingContext2D(std::unique_ptr<ImageBuffer>, bool hasAlphaChannel);
 
     std::unique_ptr<ImageBuffer> m_imageBuffer;
+    bool m_hasAlphaChannel;
 };
 
 } // namespace blink
 
 #endif // PaintRenderingContext2D_h