1860941 - Don't call GetProp in LazyInstantiator::EnableBlindAggregation if a11y is enabled

Status: RESOLVED FIXED

(Core :: Disability Access APIs, task)

Description

[James Teh [:Jamie]]

When a11y is disabled, LazyInstantiator::GetRootAccessible will return a LazyInstantiator instead of a real MsaaRootAccessible. It disables blind aggregation temporarily when it does this so that COM interface marshaling can occur without unintentionally instantiating a11y. Once marshaling is done, nsWindow calls EnableBlindAggregation to re-enable it. EnableBlindAggregation needs to query the HWND to get its associated LazyInstantiator. It does this using GetProp.

I've seen this GetProp call show up in profiles when clients are responding to a flood of events. But once a11y is enabled, GetRootAccessible returns a real MsaaRootAccessible anyway, not a LazyInstantiator. Therefore, there's no reason for EnableBlindAggregation to call GetProp at all because there's no LazyInstantiator to enable blind aggregation for.

We should just return early in this case and avoid the GetProp call.

Comment 1

[James Teh [:Jamie]]

Attachment: Bug 1860941: Don't pointlessly call GetProp in EnableBlindAggregation if there's no LazyInstantiator on which blind aggregation needs to be enabled.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/38841aca565f
Don't pointlessly call GetProp in EnableBlindAggregation if there's no LazyInstantiator on which blind aggregation needs to be enabled. r=morgan

Comment 3

[Cristina Horotan [:chorotan]]

https://hg.mozilla.org/mozilla-central/rev/38841aca565f