Issue #2175 cleanups after review

Improve ws error handling by splitting processError into handling for
errors from the network and errors from the application.

Signed-off-by: Greg Wilkins <gregw@webtide.com>

jetty-websocket/websocket-core/src/main/java/org/eclipse/jetty/websocket/core/internal/FrameFlusher.java

@@ -18,6 +18,7 @@
 
 package org.eclipse.jetty.websocket.core.internal;
 
+import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
@@ -74,6 +75,18 @@ public class FrameFlusher extends IteratingCallback
         }
     }
 
+    public void onClose()
+    {
+        Throwable cause = null;
+        synchronized (this)
+        {
+            if (!queue.isEmpty())
+                cause = new IOException("Closed");
+        }
+        if (cause!=null)
+            onCompleteFailure(cause);
+    }
+
     @Override
     protected Action process() throws Throwable
     {

jetty-websocket/websocket-core/src/main/java/org/eclipse/jetty/websocket/core/internal/WebSocketConnection.java

@@ -172,10 +172,12 @@ public class WebSocketConnection extends AbstractConnection implements Connectio
             IOException e = new IOException("Closed");
             channel.onClosed(e);
         }
+        flusher.onClose();
 
         super.onClose();
     }
 
+
     @Override
     public boolean onIdleExpired()
     {