Update extension documentation

This is a follow-up to change I1cd258e3a861236a0e1913076f222d7521830976.

Bug: 111381617
Test: N/A
Change-Id: Ie26c7dc98b54e24ae4ef6ff576440f70d0ee3fb8
Merged-In: Ie26c7dc98b54e24ae4ef6ff576440f70d0ee3fb8
(cherry picked from commit 773f03569b88e6690de59bb3ad382b1aacdef15b)
2 files changed