Added the framework for having canvas/recorder/picture record depth_set's.

src/core/SkPictureRecord.h

Index: src/core/SkPictureRecord.h
diff --git a/src/core/SkPictureRecord.h b/src/core/SkPictureRecord.h
index 8504c00ee4fdd553ec32169d1e79f40ff01a2386..f0f70cd78bf6cb9bbd8926819c64cb30fc16ec56 100644
--- a/src/core/SkPictureRecord.h
+++ b/src/core/SkPictureRecord.h
@@ -159,6 +159,8 @@ protected:
     void didConcat(const SkMatrix&) override;
     void didSetMatrix(const SkMatrix&) override;
 
+    void didSetZ(SkScalar) override;
+
     void onDrawDRRect(const SkRRect&, const SkRRect&, const SkPaint&) override;
 
     void onDrawText(const void* text, size_t, SkScalar x, SkScalar y, const SkPaint&) override;