[FIXED JENKINS-13625]

In the end, proper fix requires having a filter that tracks
GZipOutputStream.

core/pom.xml

@@ -42,7 +42,7 @@ THE SOFTWARE.
 
   <properties>
     <staplerFork>true</staplerFork>
-    <stapler.version>1.188</stapler.version>
+    <stapler.version>1.189</stapler.version>
   </properties>
 
   <dependencies>

core/src/main/java/hudson/security/HudsonAuthenticationEntryPoint.java

@@ -82,16 +82,7 @@ public class HudsonAuthenticationEntryPoint extends AuthenticationProcessingFilt
             rsp.setContentType("text/html;charset=UTF-8");
             PrintWriter out;
             try {
-                OutputStream sout = rsp.getOutputStream();
-//                if (rsp.containsHeader("Content-Encoding")) {
-//                    // we serve Jelly pages with Content-Encoding:gzip.
-//                    // ServletResponse doesn't provide means for us to check the value of the header,
-//                    // to make the matter worse, GZIPOutputStream writes a header right away,
-//                    // so by the time we get here we already have GZip header. Skip that part away by skipping first 10 bytes.
-//                    // this is a hack.
-//                    sout = new GZIPOutputStream(new ChopHeaderOutputStream(sout,10));
-//                }
-                out = new PrintWriter(new OutputStreamWriter(sout));
+                out = new PrintWriter(new OutputStreamWriter(rsp.getOutputStream()));
             } catch (IllegalStateException e) {
                 out = rsp.getWriter();
             }
@@ -110,32 +101,4 @@ public class HudsonAuthenticationEntryPoint extends AuthenticationProcessingFilt
             out.close();
         }
     }
-
-    private static class ChopHeaderOutputStream extends FilterOutputStream {
-        private int count;
-
-        ChopHeaderOutputStream(OutputStream out, int count) {
-            super(out);
-            this.count = count;
-        }
-        
-        @Override
-        public void write(byte[] b, int off, int len) throws IOException {
-            int i = Math.min(len,count);
-            count-=i;
-            off+=i;
-            len-=i;
-
-            if (len>0)
-                out.write(b, off, len);
-        }
-
-        @Override
-        public void write(int b) throws IOException {
-            if (count>0)
-                count--;
-            else
-                out.write(b);
-        }
-    }
 }

core/src/main/java/jenkins/model/Jenkins.java

@@ -2997,6 +2997,13 @@ public class Jenkins extends AbstractCIBase implements ModifiableItemGroup<TopLe
         rsp.getWriter().println("GCed");
     }
 
+    /**
+     * End point that intentionally throws an exception to test the error behaviour.
+     */
+    public void doException() {
+        throw new RuntimeException();
+    }
+
     public ContextMenu doContextMenu(StaplerRequest request, StaplerResponse response) throws IOException, JellyException {
         return new ContextMenu().from(this,request,response);
     }

war/src/main/webapp/WEB-INF/web.xml

@@ -48,6 +48,10 @@ THE SOFTWARE.
     <filter-name>encoding-filter</filter-name>
     <filter-class>hudson.util.CharacterEncodingFilter</filter-class>
   </filter>
+  <filter>
+    <filter-name>compression-filter</filter-name>
+    <filter-class>org.kohsuke.stapler.compression.CompressionFilter</filter-class>
+  </filter>
   <filter>
     <filter-name>authentication-filter</filter-name>
     <filter-class>hudson.security.HudsonFilter</filter-class>
@@ -110,6 +114,10 @@ THE SOFTWARE.
     <filter-name>encoding-filter</filter-name>
     <url-pattern>/*</url-pattern>
   </filter-mapping>
+  <filter-mapping>
+    <filter-name>compression-filter</filter-name>
+    <url-pattern>/*</url-pattern>
+  </filter-mapping>
   <filter-mapping>
     <filter-name>authentication-filter</filter-name>
     <url-pattern>/*</url-pattern>