Tabs:Lazy Rendering With Keep Mounted

Build 2896 on improve-tabs
Reviewing disabled
Baseline History
Build 28968fa9a5f
Current build. There are unaccepted changes, so build 2889 is still the baseline.
Build 2889044f219 current baseline
Accepted by Andrey Yamanov.
Build 286336783e8
Accepted by Andrey Yamanov.
Build 2845aa4065d
Auto-accepted
Commenting is disabled because there's a newer build on this branch