Revert of Remove SK_SUPPORT_LEGACY_DEEPFLATTENING.

src/opts/SkXfermode_opts_SSE2.cpp

Index: src/opts/SkXfermode_opts_SSE2.cpp
diff --git a/src/opts/SkXfermode_opts_SSE2.cpp b/src/opts/SkXfermode_opts_SSE2.cpp
index fccf66514789950d58da06f9695af0fb90d4409a..02ca0382dd8b91f7b843107073ffdf65038fa30e 100644
--- a/src/opts/SkXfermode_opts_SSE2.cpp
+++ b/src/opts/SkXfermode_opts_SSE2.cpp
@@ -641,6 +641,13 @@
 
 extern SkXfermodeProcSIMD gSSE2XfermodeProcs[];
 
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+SkSSE2ProcCoeffXfermode::SkSSE2ProcCoeffXfermode(SkReadBuffer& buffer) : INHERITED(buffer) {
+    fProcSIMD = reinterpret_cast<void*>(gSSE2XfermodeProcs[this->getMode()]);
+    buffer.validate(fProcSIMD != NULL);
+}
+#endif
+
 void SkSSE2ProcCoeffXfermode::xfer32(SkPMColor dst[], const SkPMColor src[],
                                      int count, const SkAlpha aa[]) const {
     SkASSERT(dst && src && count >= 0);