Fill incomplete images in SkCodec parent class

src/codec/SkMaskSwizzler.h

Index: src/codec/SkMaskSwizzler.h
diff --git a/src/codec/SkMaskSwizzler.h b/src/codec/SkMaskSwizzler.h
index fbc951a070806e954896e56913e863360ca398ee..6348bcc6bc7774a81a531e504dc0059e4298f369 100644
--- a/src/codec/SkMaskSwizzler.h
+++ b/src/codec/SkMaskSwizzler.h
@@ -51,6 +51,10 @@ private:
 
     int onSetSampleX(int) override;
 
+    int onGetScaledWidth() override {
+        return fDstWidth;
+    }
+
     SkMasks*        fMasks;           // unowned
     const RowProc   fRowProc;