Revert of Remove SK_SUPPORT_LEGACY_DEEPFLATTENING.

src/effects/SkAlphaThresholdFilter.cpp

Index: src/effects/SkAlphaThresholdFilter.cpp
diff --git a/src/effects/SkAlphaThresholdFilter.cpp b/src/effects/SkAlphaThresholdFilter.cpp
index ffdba322649a30ebd4cec24f37e57364ca038f4c..e1816754092ac52378dc827de1f31b6f6a77456a 100644
--- a/src/effects/SkAlphaThresholdFilter.cpp
+++ b/src/effects/SkAlphaThresholdFilter.cpp
@@ -19,6 +19,9 @@
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkAlphaThresholdFilterImpl)
 
 protected:
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+    explicit SkAlphaThresholdFilterImpl(SkReadBuffer& buffer);
+#endif
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const Context&,
@@ -233,6 +236,15 @@
     }
 }
 
+#endif
+
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+SkAlphaThresholdFilterImpl::SkAlphaThresholdFilterImpl(SkReadBuffer& buffer)
+  : INHERITED(1, buffer) {
+    fInnerThreshold = buffer.readScalar();
+    fOuterThreshold = buffer.readScalar();
+    buffer.readRegion(&fRegion);
+}
 #endif
 
 SkFlattenable* SkAlphaThresholdFilterImpl::CreateProc(SkReadBuffer& buffer) {