Add kjellander@webrtc.org to more OWNERS for BUILD.gn files.

TBR=henrika@webrtc.org
NOTRY=True

Review-Url: https://codereview.webrtc.org/2294883008
Cr-Original-Commit-Position: refs/heads/master@{#14045}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c0f28be1ca5d5423d69d5019ce4d1717e75d15a9