Fix image resizing bug.

If the image was already smaller than the treshold, it was
trying to re-use a buffer that was already consumed.

Change-Id: Ifb61fe0bae401462188a8e08ddf2937c7080c4df

server/go/camlistored/image.go

@@ -68,7 +68,11 @@ func (ih *ImageHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request, fil
 
 	var buf bytes.Buffer
 	n, err := io.Copy(&buf, fr)
-	i, format, err := image.Decode(&buf)
+	if err != nil {
+		log.Printf("image resize: error reading image %s: %v", file, err)
+		return
+	}
+	i, format, err := image.Decode(bytes.NewBuffer(buf.Bytes()))
 	if err != nil {
 		http.Error(rw, "Can't serve file: "+err.String(), 500)
 		return

server/go/camlistored/publish.go

@@ -464,6 +464,7 @@ func (pr *publishRequest) serveSubresFileDownload() {
 func (pr *publishRequest) serveScaledImage(des *search.DescribedBlob, maxWidth, maxHeight int) {
 	fileref, _, ok := pr.fileSchemaRefFromBlob(des)
 	if !ok {
+		log.Printf("scaled image fail; failed to get file schema from des %q", des.BlobRef)
 		return
 	}
 	th := &ImageHandler{