Add seantopping to some chromecast/ owners files

Bug: none
Change-Id: I33a08288c678b9a3d6d40eecbf5144b049f97cdf
Reviewed-on: https://chromium-review.googlesource.com/c/1428719
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Luke Halliwell <halliwell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625320}
3 files changed