Fill incomplete images in SkCodec parent class

src/codec/SkWebpCodec.cpp

Index: src/codec/SkWebpCodec.cpp
diff --git a/src/codec/SkWebpCodec.cpp b/src/codec/SkWebpCodec.cpp
index ccf49649edb30e669c1b497f94b0e3cb69eeec0d..5a0753c731567a75b4813ce1e943538c2f28aa6c 100644
--- a/src/codec/SkWebpCodec.cpp
+++ b/src/codec/SkWebpCodec.cpp
@@ -231,10 +231,10 @@ SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst,
     while (true) {
         const size_t bytesRead = stream()->read(buffer, BUFFER_SIZE);
         if (0 == bytesRead) {
-            // FIXME: Maybe this is an incomplete image? How to decide? Based
-            // on the number of rows decoded? We can know the number of rows
-            // decoded using WebPIDecGetRGB.
-            return kInvalidInput;
+            int rowsDecoded;
+            WebPIDecGetRGB(idec, &rowsDecoded, NULL, NULL, NULL);
+            this->setIncompleteScanlines(dstDimensions.height() - rowsDecoded);
+            return kIncompleteInput;
         }
 
         switch (WebPIAppend(idec, buffer, bytesRead)) {