450873 Disable tests that downcaste wrapped GzipFilterResponses

jetty-servlets/src/test/java/org/eclipse/jetty/servlets/GzipFilterContentLengthTest.java

@@ -344,9 +344,10 @@ public class GzipFilterContentLengthTest
      * @see <a href="Eclipse Bug 450873">http://bugs.eclipse.org/450873</a>
      */
     @Test
-    @Ignore
     public void testHttpOutputWrite() throws Exception
     {
+        if (gzipFilterClass == GzipFilter.class)
+            return;  // Can't downcaste output stream when wrapper is used
         testWithGzip(TestServletBufferTypeLengthWrite.class);
     }
 }

jetty-servlets/src/test/java/org/eclipse/jetty/servlets/gzip/TestServletBufferTypeLengthWrite.java

@@ -61,7 +61,7 @@ public class TestServletBufferTypeLengthWrite extends TestDirContentServlet
         response.setHeader("ETag","W/etag-"+fileName);
 
         response.setContentLength(dataBytes.length);
-
+        
         ((HttpOutput)out).write(ByteBuffer.wrap(dataBytes).asReadOnlyBuffer());
     }
 }