Relieve unwanted pressure on the web socket wrapper queue that caused huge memory spikes (this loop would be very fast and cause tons of actions to be scheduled when there should be none). Issue #990

Author: borrrden

src/Couchbase.Lite.Shared/Sync/WebSocketWrapper.cs

@@ -392,6 +392,13 @@ private void PerformRead()
 
                     // Phew, at this point we are clear to actually read from the stream
                     var received = stream.Read(_buffer, 0, _buffer.Length);
+                    if (received == 0) {
+                        // Should only happen on a closed stream, but just in case let's continue
+                        // after a small delay (wait for cancellation to confirm)
+                        Thread.Sleep(200);
+                        continue;
+                    }
+
                     var data = _buffer.Take(received).ToArray();
                     Receive(data);
                 } catch (Exception e) {