Revert of factories should return baseclass, allowing the impl to specialize

src/effects/SkRectShaderImageFilter.cpp

Index: src/effects/SkRectShaderImageFilter.cpp
diff --git a/src/effects/SkRectShaderImageFilter.cpp b/src/effects/SkRectShaderImageFilter.cpp
index 14837d02b15680268368d06eb635bbc865392167..f9e70705c51e468018055d87ade9ae910e43a3ad 100644
--- a/src/effects/SkRectShaderImageFilter.cpp
+++ b/src/effects/SkRectShaderImageFilter.cpp
@@ -13,7 +13,7 @@
 #include "SkWriteBuffer.h"
 #include "SkShader.h"
 
-SkImageFilter* SkRectShaderImageFilter::Create(SkShader* s, const SkRect& rect) {
+SkRectShaderImageFilter* SkRectShaderImageFilter::Create(SkShader* s, const SkRect& rect) {
     SkASSERT(s);
     uint32_t flags = CropRect::kHasAll_CropEdge;
     if (rect.width() == 0 || rect.height() == 0) {
@@ -23,7 +23,7 @@
     return s ? new SkRectShaderImageFilter(s, &cropRect) : nullptr;
 }
 
-SkImageFilter* SkRectShaderImageFilter::Create(SkShader* s, const CropRect* cropRect) {
+SkRectShaderImageFilter* SkRectShaderImageFilter::Create(SkShader* s, const CropRect* cropRect) {
     SkASSERT(s);
     return s ? new SkRectShaderImageFilter(s, cropRect) : nullptr;
 }