Revert of Moving SkBlurImageFilter into core

include/core/SkImageFilter.h

Index: include/core/SkImageFilter.h
diff --git a/include/core/SkImageFilter.h b/include/core/SkImageFilter.h
index 97f84dc596720a2176869b1e97a63adfcb3c41c1..6210073bf4a4c6e317a8a814d79eed5ca1bc68c0 100644
--- a/include/core/SkImageFilter.h
+++ b/include/core/SkImageFilter.h
@@ -152,10 +152,6 @@
         return this->isColorFilterNode(filterPtr);
     }
 
-    static sk_sp<SkImageFilter> MakeBlur(SkScalar sigmaX, SkScalar sigmaY,
-                                         sk_sp<SkImageFilter> input,
-                                         const CropRect* cropRect = nullptr);
-
     /**
      *  Returns true (and optionally returns a ref'd filter) if this imagefilter can be completely
      *  replaced by the returned colorfilter. i.e. the two effects will affect drawing in the
@@ -233,7 +229,6 @@
 
     SK_TO_STRING_PUREVIRT()
     SK_DEFINE_FLATTENABLE_TYPE(SkImageFilter)
-    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 
 protected:
     class Common {