Fill incomplete images in SkCodec parent class

src/codec/SkCodec_libgif.h

Index: src/codec/SkCodec_libgif.h
diff --git a/src/codec/SkCodec_libgif.h b/src/codec/SkCodec_libgif.h
index 88455368512efb47766b9c06aeb16a18a9eeb99a..42571ad4943a9d05ab03287dd8664d6f9da424b7 100644
--- a/src/codec/SkCodec_libgif.h
+++ b/src/codec/SkCodec_libgif.h
@@ -63,7 +63,7 @@ protected:
      * Performs the full gif decode
      */
     Result onGetPixels(const SkImageInfo&, void*, size_t, const Options&,
-            SkPMColor*, int32_t*) override;
+            SkPMColor*, int*, int*) override;
 
     SkEncodedFormat onGetEncodedFormat() const override {
         return kGIF_SkEncodedFormat;
@@ -71,6 +71,8 @@ protected:
 
     bool onRewind() override;
 
+    uint32_t onGetFillValue(const SkImageInfo& dstInfo) const override;
+
 private:
 
     /*
@@ -129,10 +131,9 @@ private:
             ZeroInitialized zeroInit);
 
     /*
-     * @return kSuccess if the read is successful and kIncompleteInput if the
-     *         read fails.
+     * @return true if the read is successful and false if the read fails.
      */
-    SkCodec::Result readRow();
+    bool readRow();
 
     /*
      * This function cleans up the gif object after the decode completes