Why am I seeing warnings about synchronous XMLHttpRequests being deprecated when JavaScript Streaming is enabled?

When using browser developer tools when JavaScript Streaming is enabled, you will see warnings about synchronous XMLHttpRequests being deprecated because of their detrimental effects to the end user's experience. This is expected behavior and shows that JavaScript Streaming is doing its job by demand-loading code when needed.

The message comes from the browser developer tools. General use of synchronous XHRs is not recommended, so the developer tools are being helpful to suggest this. But JavaScript Streaming relies on synchronous XHR calls to ensure that function misses are handled when they occur. This message is purely a warning and does not have any effect on the script's execution.