Add a basic custom painting facility to Sky

sky/engine/platform/graphics/DisplayList.h

Index: sky/engine/platform/graphics/DisplayList.h
diff --git a/sky/engine/platform/graphics/DisplayList.h b/sky/engine/platform/graphics/DisplayList.h
index 4161a3e6b354dc9c3c5ea5db1078b4f35f011a9c..fcf13ff0ee87cac4aff031d78a3fc4e3f4b1b0cb 100644
--- a/sky/engine/platform/graphics/DisplayList.h
+++ b/sky/engine/platform/graphics/DisplayList.h
@@ -49,11 +49,9 @@ class PLATFORM_EXPORT DisplayList final : public WTF::RefCounted<DisplayList> {
     WTF_MAKE_FAST_ALLOCATED;
     WTF_MAKE_NONCOPYABLE(DisplayList);
 public:
-    DisplayList(const FloatRect&);
+    DisplayList();
     ~DisplayList();
 
-    const FloatRect& bounds() const;
-
     // This entry point will return 0 when the DisplayList is in the
     // midst of recording (i.e., between a beginRecording/endRecording pair)
     // and if no recording has ever been completed. Otherwise it will return
@@ -65,7 +63,6 @@ public:
     void endRecording();
 
 private:
-    FloatRect m_bounds;
     RefPtr<SkPicture> m_picture;
     OwnPtr<SkPictureRecorder> m_recorder;
 };