Add nested SkPictureImageFilters to the GPU veto.

src/effects/SkPictureImageFilter.cpp

Index: src/effects/SkPictureImageFilter.cpp
diff --git a/src/effects/SkPictureImageFilter.cpp b/src/effects/SkPictureImageFilter.cpp
index bfe26b62c556b165e5c1d788b7749ca7c69f98e1..473a92a94079e2acfd3c420c5df2e0e80b41eb5b 100644
--- a/src/effects/SkPictureImageFilter.cpp
+++ b/src/effects/SkPictureImageFilter.cpp
@@ -201,6 +201,10 @@ void SkPictureImageFilter::drawPictureAtLocalResolution(SkSpecialImage* source,
     }
 }
 
+int SkPictureImageFilter::numSlowPaths() const {
+    return fPicture ? fPicture->numSlowPaths() : 0;
+}
+
 #ifndef SK_IGNORE_TO_STRING
 void SkPictureImageFilter::toString(SkString* str) const {
     str->appendf("SkPictureImageFilter: (");