Create special surfaces according to original device (not always in N32)

src/effects/SkDropShadowImageFilter.cpp

Index: src/effects/SkDropShadowImageFilter.cpp
diff --git a/src/effects/SkDropShadowImageFilter.cpp b/src/effects/SkDropShadowImageFilter.cpp
index 5befe711942746819abd8ce579ec9a540fdd67b2..b4b8cac4f0c95a9b0f5b1e6b60d80bd345d9010a 100644
--- a/src/effects/SkDropShadowImageFilter.cpp
+++ b/src/effects/SkDropShadowImageFilter.cpp
@@ -77,9 +77,7 @@ sk_sp<SkSpecialImage> SkDropShadowImageFilter::onFilterImage(SkSpecialImage* sou
         return nullptr;
     }
 
-    const SkImageInfo info = SkImageInfo::MakeN32(bounds.width(), bounds.height(),
-                                                  kPremul_SkAlphaType);
-    sk_sp<SkSpecialSurface> surf(source->makeSurface(info));
+    sk_sp<SkSpecialSurface> surf(source->makeSurface(ctx.outputProperties(), bounds.size()));
     if (!surf) {
         return nullptr;
     }