1963917 - Ignore the TAO check for cross origin images for LCP

Status: RESOLVED FIXED

(Core :: DOM: Performance APIs, enhancement)

Description

[Sean Feng [:sefeng211]]

There was an update to LCP spec such that the renderTime is no longer
protected by Timing-Allow-Origin due to it's easy to side channel attack
it and it isn't needed for CORS protected images.

The solution was to coarsen the timestamp by 4ms (this is what Chrome did).

To do something similar in Firefox, we don't need to coarsen the
timestamp because we already reduce more precisions. We just need to
always expose this.

Spec discussion: https://github.com/w3c/largest-contentful-paint/issues/111

This patch won't fix any test, instead, it'll make multiple-redirects-TAO.html starts to depend on PaintTimingMixin

Comment 1

[Sean Feng [:sefeng211]]

Attachment: Bug 1963917 - Ignore the TAO check for cross origin images for LCP

There was an update to LCP spec such that the renderTime is no longer
protected by Timing-Allow-Origin due to it's easy to side channel attack
it and it isn't needed for CORS protected images.

The solution was to coarsen the timestamp by 4ms (this is what Chrome did).

To do something similar in Firefox, we don't need to coarsen the
timestamp because we already reduce more precisions. We just need to
always expose this.

Spec discussion: https://github.com/w3c/largest-contentful-paint/issues/111

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/36a5e41c7ceb
Ignore the TAO check for cross origin images for LCP r=mstange

Comment 3

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/36a5e41c7ceb

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/6e45200ba360
Revert "Bug 1963917 - Ignore the TAO check for cross origin images for LCP r=mstange" for causing wpt failures

Comment 5

[amarc]

Backed out for causing wpt failures

• Backout link
• Push with failures
• Failure Log 1
• Failure Log 2

Comment 6

[Sean Feng [:sefeng211]]

Ah right, we fixed bug 1963464, so more tests are passing.

Comment 7

[Serban Stanca [:SerbanS]]

Backout got merged in central: https://hg.mozilla.org/mozilla-central/rev/6e45200ba360194bb2bc2a158bd312ba768a4548

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c3ac0c48fcab
Ignore the TAO check for cross origin images for LCP r=mstange

Comment 9

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/c3ac0c48fcab