Report 0 rowsDecoded for no rows (SkPngCodec interlaced)

src/codec/SkPngCodec.cpp

Index: src/codec/SkPngCodec.cpp
diff --git a/src/codec/SkPngCodec.cpp b/src/codec/SkPngCodec.cpp
index 0675653b82da9b86cd279f088ccc15e0a581743e..1344a7e773c6ad52c738a47aa62253f9cdce499f 100644
--- a/src/codec/SkPngCodec.cpp
+++ b/src/codec/SkPngCodec.cpp
@@ -764,6 +764,9 @@ private:
 
         // Now apply Xforms on all the rows that were decoded.
         if (!fLinesDecoded) {
+            if (rowsDecoded) {
+                *rowsDecoded = 0;
+            }
             return SkCodec::kIncompleteInput;
         }
         const int lastRow = fLinesDecoded + fFirstRow - 1;