Simplify flattening to just write enough to call the factory

src/effects/SkLayerRasterizer.cpp

Index: src/effects/SkLayerRasterizer.cpp
diff --git a/src/effects/SkLayerRasterizer.cpp b/src/effects/SkLayerRasterizer.cpp
index 9b7bdca3f4b7fb198ff0d4ec1949144d17aac055..b331a0363df90bcabed0bc47abb124157e8f3cae 100644
--- a/src/effects/SkLayerRasterizer.cpp
+++ b/src/effects/SkLayerRasterizer.cpp
@@ -148,12 +148,18 @@ bool SkLayerRasterizer::onRasterize(const SkPath& path, const SkMatrix& matrix,
     return true;
 }
 
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
 SkLayerRasterizer::SkLayerRasterizer(SkReadBuffer& buffer)
     : SkRasterizer(buffer), fLayers(ReadLayers(buffer)) {}
+#endif
+
+SkFlattenable* SkLayerRasterizer::CreateProc(SkReadBuffer& buffer) {
+    return SkNEW_ARGS(SkLayerRasterizer, (ReadLayers(buffer)));
+}
 
 SkDeque* SkLayerRasterizer::ReadLayers(SkReadBuffer& buffer) {
     int count = buffer.readInt();
-
+    
     SkDeque* layers = SkNEW_ARGS(SkDeque, (sizeof(SkLayerRasterizer_Rec)));
     for (int i = 0; i < count; i++) {
         SkLayerRasterizer_Rec* rec = (SkLayerRasterizer_Rec*)layers->push_back();