Simplify flattening to just write enough to call the factory

src/effects/SkOffsetImageFilter.cpp

Index: src/effects/SkOffsetImageFilter.cpp
diff --git a/src/effects/SkOffsetImageFilter.cpp b/src/effects/SkOffsetImageFilter.cpp
index 57f36db113ca066c6bcb00019c17eb53076659a6..108c8bf538dd9d7ebdb07c2f948faf7dd039693b 100644
--- a/src/effects/SkOffsetImageFilter.cpp
+++ b/src/effects/SkOffsetImageFilter.cpp
@@ -91,6 +91,13 @@ bool SkOffsetImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm
     return true;
 }
 
+SkFlattenable* SkOffsetImageFilter::CreateProc(SkReadBuffer& buffer) {
+    SK_IMAGEFILTER_UNFLATTEN_COMMON(1);
+    SkPoint offset;
+    buffer.readPoint(&offset);
+    return Create(offset.x(), offset.y(), common.inputAt(0), &common.cropRect());
+}
+
 void SkOffsetImageFilter::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writePoint(fOffset);
@@ -102,9 +109,11 @@ SkOffsetImageFilter::SkOffsetImageFilter(SkScalar dx, SkScalar dy, SkImageFilter
     fOffset.set(dx, dy);
 }
 
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
 SkOffsetImageFilter::SkOffsetImageFilter(SkReadBuffer& buffer)
   : INHERITED(1, buffer) {
     buffer.readPoint(&fOffset);
     buffer.validate(SkScalarIsFinite(fOffset.fX) &&
                     SkScalarIsFinite(fOffset.fY));
 }
+#endif