Creating framework for drawShadowedPicture

include/core/SkCanvas.h

Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index 35a8d1c7b92193a4d247a4766efe54a2976ce0a6..971c108b91c425381530dfe783cb6bb91eea1679 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -17,6 +17,7 @@
 #include "SkRegion.h"
 #include "SkSurfaceProps.h"
 #include "SkXfermode.h"
+#include "SkLights.h"
 
 class GrContext;
 class GrDrawContext;
@@ -1049,6 +1050,16 @@ public:
         this->drawPicture(picture.get(), matrix, paint);
     }
 
+    /**
+     *  Draw the picture into this canvas.
+     *
+     *  However, this time, we will use the passed-in lights to generate shadows!

[jvanverth1, 2016/07/14 17:27:09]

This is a little too vague. Suggestion: Will use the list of lights and the
picture content to generate shadow maps for each light. Even that might not be
enough detail.

[vjiaoblack, 2016/07/14 20:38:17]

Done.

+     */
+    void drawShadowedPicture(const SkPicture*, sk_sp<SkLights>);

[jvanverth1, 2016/07/14 17:27:09]

Do we not need a matrix or paint?

[vjiaoblack, 2016/07/14 20:38:18]

I originally thought the proposed function didn't, but I realized that's just
pseudocode. Fixing...

+    void drawShadowedPicture(const sk_sp<SkPicture>& picture, sk_sp<SkLights> lights) {
+        this->drawShadowedPicture(picture.get(), lights);
+    }
+
     enum VertexMode {
         kTriangles_VertexMode,
         kTriangleStrip_VertexMode,
@@ -1402,6 +1413,7 @@ protected:
     virtual void onDiscard();
 
     virtual void onDrawPicture(const SkPicture*, const SkMatrix*, const SkPaint*);
+    virtual void onDrawShadowedPicture(const SkPicture*, sk_sp<SkLights>);
 
     // Returns the canvas to be used by DrawIter. Default implementation
     // returns this. Subclasses that encapsulate an indirect canvas may