The original issue were happened when only sending GamepadAdded events to the first GamepadEventChannel. That makes the later content processes would not have the existing gamepad objects. Therefore, I think we should send extra GamepadAdded events for the later GamepadEventChannels.
Bug 1538805 Comment 5 Edit History
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The original issue was happened when only sending GamepadAdded events to the first GamepadEventChannel. That makes the later content processes would not have the existing gamepad objects. Therefore, I think we should send extra GamepadAdded events for the later GamepadEventChannels.