[Webkit-unassigned] [Bug 198481] New: Loading script blocks rendering on Mobile Safari

Mon Jun 3 01:32:13 PDT 2019

https://bugs.webkit.org/show_bug.cgi?id=198481

            Bug ID: 198481
           Summary: Loading script blocks rendering on Mobile Safari
           Product: WebKit
           Version: Other
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: ambar.lee at gmail.com
                CC: bfulgham at webkit.org, simon.fraser at apple.com,
                    zalan at apple.com

Demo:

https://github.com/ambar/safari-render-blocking-bug/blob/master/views/demo.pug

```html
<body>
  <pre id="firstAFLog"></pre>
  <script>
    requestAnimationFrame(function() {
      firstAFLog.textContent = Date.now() - performance.timing.navigationStart
    })
  </script>
  <script src="/empty.js?networkDelay=2000"></script>
</body>
```

```
## iOS 11.4 Mobile Safari

| method             | firstAF | 
| ------------------ | ------- | 
| script[defer]+hack | 499     | 
| script[async]      | 499     | 
| script[async]+hack | 501     | 
| script+hack        | 504     | 
| script[defer]      | 2039    | 
| script             | 2045    | 

## iOS 12.2 Mobile Safari

| method             | firstAF | 
| ------------------ | ------- | 
| script[async]+hack | 232     | 
| script[defer]+hack | 313     | 
| script+hack        | 320     | 
| script[defer]      | 2042    | 
| script[async]      | 2045    | 
| script             | 2046    | 

## Desktop Safari (Version/12.1.1 Safari/605.1.15)

| method             | firstAF | 
| ------------------ | ------- | 
| script[async]+hack | 37      | 
| script[defer]+hack | 37      | 
| script[defer]      | 38      | 
| script+hack        | 38      | 
| script[async]      | 38      | 
| script             | 38      | 

```

*firstAF*: first animation frame time.

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