Revert of Remove SK_SUPPORT_LEGACY_DEEPFLATTENING.

src/core/SkPathEffect.cpp

Index: src/core/SkPathEffect.cpp
diff --git a/src/core/SkPathEffect.cpp b/src/core/SkPathEffect.cpp
index 7338789de2e873cb8d0461b58ae8729a8204280e..d0748670e36b3727d1d4d56ceb3e8b8369909687 100644
--- a/src/core/SkPathEffect.cpp
+++ b/src/core/SkPathEffect.cpp
@@ -49,6 +49,14 @@
     buffer.writeFlattenable(fPE1);
 }
 
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
+SkPairPathEffect::SkPairPathEffect(SkReadBuffer& buffer) {
+    fPE0 = buffer.readPathEffect();
+    fPE1 = buffer.readPathEffect();
+    // either of these may fail, so we have to check for nulls later on
+}
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 
 SkFlattenable* SkComposePathEffect::CreateProc(SkReadBuffer& buffer) {