Web Inspector: Canvas recordings use a lot of memory and are never released

• Component: Web Inspector
• Status: NEW ---

[BJ Burg]

via Nelson Thachuk:

* SUMMARY
- Canvas Tab: high resource usage when recording/after completing recording

* STEPS TO REPRODUCE
1. Launch Safari
2. Navigate to https://www.google.com/maps/place/Apple+Infinite+Loop/@37.3316756,-122.0323777,17z/data=!3m1!4b1!4m5!3m4!1s0x808fb5b6c4951d0f:0xb651414deb31e9fb!8m2!3d37.3316756!4d-122.030189
3. Show Web Inspector (⌥⌘I)
4. Click New Tab button
5. Select Canvas tab
6. Launch Activity Monitor
7. Filter by “Safari”
8. Return to Safari and record the Canvas
9. Interact with Google Maps (NOTE: the Web Content processes’ CPU usage spikes)
10. Wait for recording to finish (NOTE: the Web Content processes’ CPU usage returns to normal and Web Inspector’s processes’ Memory usage spikes)
11. Dismiss the recording or close the Canvas tab and wait 30 seconds

* EXPECTED RESULTS
- Memory should be released

* ACTUAL RESULTS
- Memory is not released until the Web Inspector process is killed

[BJ Burg]

<rdar://problem/35893620>

[BJ Burg]

The resource usage is somewhat expected, though we should have some way to clear recordings from memory if we don't expect to ever see them again. I don't know in what cases this would make sense.

After navigating, clear if:
- User never opened the recording
- Canvas Tab is closed
- Web Inspector is closed

Preserve recording if:
- User has opened it at least once
- It is imported from file
- Relevant canvas has been deleted from DOM but page hasn't navigated