Revert of Remove SK_SUPPORT_LEGACY_DEEPFLATTENING.

src/effects/SkXfermodeImageFilter.cpp

Index: src/effects/SkXfermodeImageFilter.cpp
diff --git a/src/effects/SkXfermodeImageFilter.cpp b/src/effects/SkXfermodeImageFilter.cpp
index 1618b640360a1369bfb08eefe19061d0a73a4eca..379d6d8f9578fe733bbdc9d9c8291308958d261f 100644
--- a/src/effects/SkXfermodeImageFilter.cpp
+++ b/src/effects/SkXfermodeImageFilter.cpp
@@ -31,6 +31,13 @@
 SkXfermodeImageFilter::~SkXfermodeImageFilter() {
     SkSafeUnref(fMode);
 }
+
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+SkXfermodeImageFilter::SkXfermodeImageFilter(SkReadBuffer& buffer)
+  : INHERITED(2, buffer) {
+    fMode = buffer.readXfermode();
+}
+#endif
 
 SkFlattenable* SkXfermodeImageFilter::CreateProc(SkReadBuffer& buffer) {
     SK_IMAGEFILTER_UNFLATTEN_COMMON(common, 2);