Sky: Add a DrawLooper interface to the painting API to be used for shadows.

sky/engine/core/painting/DrawLooperAddLayerCallback.cpp

Index: sky/engine/core/painting/DrawLooperAddLayerCallback.cpp
diff --git a/sky/engine/core/painting/Paint.cpp b/sky/engine/core/painting/DrawLooperAddLayerCallback.cpp
similarity index 66%
copy from sky/engine/core/painting/Paint.cpp
copy to sky/engine/core/painting/DrawLooperAddLayerCallback.cpp
index f3e6fcae0fbd241cca373bde147ae83dce270c6c..fdd8c4ca8ce62bc44a443fa0a53a209e1fe30190 100644
--- a/sky/engine/core/painting/Paint.cpp
+++ b/sky/engine/core/painting/DrawLooperAddLayerCallback.cpp
@@ -3,16 +3,11 @@
 // found in the LICENSE file.
 
 #include "sky/engine/config.h"
-#include "sky/engine/core/painting/Paint.h"
+#include "sky/engine/core/painting/DrawLooperAddLayerCallback.h"
 
 namespace blink {
 
-Paint::Paint()
-{
-}
-
-Paint::~Paint()
-{
+DrawLooperAddLayerCallback::~DrawLooperAddLayerCallback() {
 }
 
 } // namespace blink