Simplify flattening to just write enough to call the factory

src/effects/SkTransparentShader.cpp

Index: src/effects/SkTransparentShader.cpp
diff --git a/src/effects/SkTransparentShader.cpp b/src/effects/SkTransparentShader.cpp
index f290d0dcf8d5c0b834b8729e519661f302f31799..aab5a3d85c78fb7185fbb4bda42452857d04fe94 100644
--- a/src/effects/SkTransparentShader.cpp
+++ b/src/effects/SkTransparentShader.cpp
@@ -115,6 +115,10 @@ void SkTransparentShader::TransparentShaderContext::shadeSpan16(int x, int y, ui
     }
 }
 
+SkFlattenable* SkTransparentShader::CreateProc(SkReadBuffer& buffer) {
+    return SkNEW(SkTransparentShader);
+}
+
 #ifndef SK_IGNORE_TO_STRING
 void SkTransparentShader::toString(SkString* str) const {
     str->append("SkTransparentShader: (");