Bugzilla

# Abstract

The API `sessions.getTabValue()` called for a duplicated tab returns a value same to the one for the original tab. However now it requires too large delay to get an expected value by a `tabs.onCreated` listener. On my environment the required delay is 400-600 msec, it is painfully slow. The required delay was 0 or less than 100msec in old versions of Firefox, thus it looks a regression by some recent changes.

# Steps to reproduce

1. Go to about:debugging.
2. Load the attached testcase XPI as a temporary addon.
   (The addon registers a listener for the `tabs.onCreated`, and tries to call `sessions.getTabValue()` for notified tabs. If it is a duplicated tab, the result must be same to the one for the original tab. This addon measures the delay required to get the value same to the original tab.)
3. Then it opens and closes many tabs. Please wait for a while.
4. After all the result is reported in the active tab.

# Actual result

The result says `640msec delay is required` (on my environment).

# Expected result

The result says `success with no delay`.

# Environment

* Windows 10 Pro 20H2
* Nightly 89.0a1 (build ID: 20210329214331)

# Bisection result

The last good build is at 6th March looks good, and the initial bad build is at 7th March.
Sadly I couldn't find out the exact build the problem started at.

# Abstract

The API `sessions.getTabValue()` called for a duplicated tab returns a value same to the one for the original tab. However now it requires too large delay to get an expected value by a `tabs.onCreated` listener. On my environment the required delay is 400-600 msec, it is painfully slow. The required delay was 0 or less than 100msec in old versions of Firefox, thus it looks a regression by some recent changes.

# Steps to reproduce

1. Go to about:debugging.
2. Load the attached testcase XPI as a temporary addon.
   (The addon registers a listener for the `tabs.onCreated`, and tries to call `sessions.getTabValue()` for notified tabs. If it is a duplicated tab, the result must be same to the one for the original tab. This addon measures the delay required to get the value same to the original tab.)
3. Then it opens and closes many tabs. Please wait for a while.
4. After all the result is reported in the active tab.

# Actual result

The result says `640msec delay is required` (on my environment).

# Expected result

The result says `success with no delay`.

# Environment

* Windows 10 Pro 20H2
* Nightly 89.0a1 (build ID: 20210329214331)

# Bisection result

The last good build is at 6th March, and the initial bad build is at 7th March.
Sadly I couldn't find out the exact build the problem started at.