Cleanup handling of BinaryResult

Simplify the logic to stack BinaryResult instances on top of each
other when applying the base64 and/or gzip transforms before writing
to the HttpServletResponse.

Change-Id: I1a477d5b9888cac981021149905a9aaa8f2f89ad

gerrit-server/src/main/java/com/google/gerrit/server/change/GetContent.java

@@ -64,7 +64,8 @@ public class GetContent implements RestReadView<FileResource> {
             public void writeTo(OutputStream os) throws IOException {
               object.copyTo(os);
             }
-          }.setContentLength(object.getSize()).base64();
+          }.setContentLength(object.getSize())
+           .base64();
         } finally {
           tw.release();
         }