Bug 187173

Summary: Preload headers not loading assets assets on parse
Product: WebKit Reporter: Robert <unknown9595>
Component: Page LoadingAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Normal CC: beidson, youennf
Priority: P2    
Version: Safari Technology Preview   
Hardware: Mac   
OS: macOS 10.13   
Attachments:
Description Flags
The JS CSS should be loaded at the beginning of the waterfall none

Description Robert 2018-06-29 03:49:05 PDT 
Created attachment 343903 [details]
The JS CSS should be loaded at the beginning of the waterfall

Steps to reproduce the problem:
1. Open Network inspector
2. I created a demo page, which flushes the preload headers, then adds a delay, then flushes the rest of the page
Go to https://glitch.com/edit/#!/thunder-tune > Show Live
3. The waterfall shows assets loaded when the HTML is fully downloaded

What is the expected behavior?
Assets should be downloaded as soon as the Preload headers are parsed. This happens regardless of if GZIPed (Comment back in compression in demo to enable GZIP).

What went wrong?
Assets are loaded once the HTML has been parsed, not when the preload headers are parsed.

Did this work before? N/A 

Does this work in other browsers? No

Not sure if this is an Express/Node issue or a browser issue, but if I curl the demo I can see the preload headers > delay > rest of HTML so content is being sent to the browser.
Have filed a Chrome issue as well, but it only affects Chrome when GZIPed.