Simplify flattening to just write enough to call the factory

include/effects/SkOffsetImageFilter.h

Index: include/effects/SkOffsetImageFilter.h
diff --git a/include/effects/SkOffsetImageFilter.h b/include/effects/SkOffsetImageFilter.h
index 7f17e851cb6ec301d77b2d96bd70a6290ff33ccc..d18dcae315efc801ff7c6f456528e50e98d71ca0 100644
--- a/include/effects/SkOffsetImageFilter.h
+++ b/include/effects/SkOffsetImageFilter.h
@@ -17,6 +17,9 @@ class SK_API SkOffsetImageFilter : public SkImageFilter {
 public:
     static SkOffsetImageFilter* Create(SkScalar dx, SkScalar dy, SkImageFilter* input = NULL,
                                        const CropRect* cropRect = NULL) {
+        if (!SkScalarIsFinite(dx) || !SkScalarIsFinite(dy)) {
+            return NULL;
+        }
         return SkNEW_ARGS(SkOffsetImageFilter, (dx, dy, input, cropRect));
     }
     virtual void computeFastBounds(const SkRect& src, SkRect* dst) const SK_OVERRIDE;
@@ -24,7 +27,9 @@ public:
 
 protected:
     SkOffsetImageFilter(SkScalar dx, SkScalar dy, SkImageFilter* input, const CropRect* cropRect);
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
     explicit SkOffsetImageFilter(SkReadBuffer& buffer);
+#endif
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const Context&,