[Media Intent Handler] Fix broken watchtime metric

This CL re-adds logic to log MediaLauncherActivity in the
WebappCustomTabTimeSpentLogger. This was accidentally removed in a
rebase.

Bug: 935777
Change-Id: Ifa553184ab3e598cd3c0787eead8845a3b4c0695
Reviewed-on: https://chromium-review.googlesource.com/c/1493441
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636483}
1 file changed