1506005 - Remove restriction that there is only one in flight paint at a time

Status: RESOLVED FIXED

(Core Graveyard :: Web Replay, enhancement)

Description

[Brian Hackett [Laid off!]]

Attachment: patch

Bug 1499186 added a restriction that we can only have one in flight paint at a time, except for repaints initiated by the debugger.  This was done to preserve the invariant that any Paint message sent by a child reflects the state at the last checkpoint, but it has also been problematic because if a paint is triggered in some way other than through a vsync, we can end up with multiple in flight paints and crash on an assertion.

The attached patch removes this restriction and allows multiple in flight paints at a time.  We still preserve the above invariant: if a new paint is started before the previous one finishes, we don't send a Paint message for the first paint when it completes.  The ability to ignore vsyncs by returning false from OnVsync is not required for correctness anymore, but I left it in as it ensures we can't get any pathological behavior where most paints overlap the previous one and the page's graphics are infrequently updated.

Comment 1

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/24370d1616e8
Remove restriction that there is only one in flight paint at a time, r=nical.

Comment 2

[Dorel Luca [:dluca]]

https://hg.mozilla.org/mozilla-central/rev/24370d1616e8