Make it possible to custom-paint without an Element.

sky/engine/core/painting/Canvas.h

 // Copyright 2015 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 SKY_ENGINE_CORE_PAINTING_PAINTINGCONTEXT_H_
-#define SKY_ENGINE_CORE_PAINTING_PAINTINGCONTEXT_H_
+#ifndef SKY_ENGINE_CORE_PAINTING_CANVAS_H_
+#define SKY_ENGINE_CORE_PAINTING_CANVAS_H_
 
 #include "sky/engine/core/painting/Paint.h"
 #include "sky/engine/platform/graphics/DisplayList.h"
 #include "sky/engine/tonic/dart_wrappable.h"
 #include "sky/engine/wtf/PassRefPtr.h"
 #include "sky/engine/wtf/RefCounted.h"
 
 namespace blink {
 class Element;
 
-class PaintingContext : public RefCounted<PaintingContext>, public DartWrappable {
+class Canvas : public RefCounted<Canvas>, public DartWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    ~PaintingContext() override;
-    static PassRefPtr<PaintingContext> create(PassRefPtr<Element> element, const FloatSize& size);
+    Canvas(const FloatSize& size);
+    ~Canvas() override;
 
+    // Width/Height define a culling rect which Skia may use for optimizing
+    // out draw calls issued outside the rect.
+    double width() const { return m_size.width(); }
     double height() const { return m_size.height(); }
-    double width() const { return m_size.width(); }
 
     void drawCircle(double x, double y, double radius, Paint* paint);

[Matt Perry, 2015/05/13 18:33:21]

Skia takes these params as SkScalars, which are floats, not doubles. Is there a
reason we chose not to use float here?

-    void commit();
+
+protected:
+    PassRefPtr<DisplayList> finishRecording();
+
+    bool isRecording() const { return m_canvas; }
 
 private:
-    PaintingContext(PassRefPtr<Element> element, const FloatSize& size);
-
-    RefPtr<Element> m_element;
     FloatSize m_size;
     RefPtr<DisplayList> m_displayList;
     SkCanvas* m_canvas;
 };
 
 } // namespace blink
 
-#endif  // SKY_ENGINE_CORE_PAINTING_PAINTINGCONTEXT_H_
+#endif  // SKY_ENGINE_CORE_PAINTING_CANVAS_H_