Add "alpha" option to PaintWorklet

third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.h

Index: third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.h
diff --git a/third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.h b/third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.h
index 03b3fa65a15a3af1ace2a25a74309149e2ab2bb5..6a64ef553a77908cbca90dc0babf69396e8dfea4 100644
--- a/third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.h
+++ b/third_party/WebKit/Source/modules/csspaint/PaintRenderingContext2D.h
@@ -23,9 +23,9 @@ class MODULES_EXPORT PaintRenderingContext2D : public BaseRenderingContext2D, pu
     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
@@ -62,15 +62,16 @@ public:
 
     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