Fix OWNERS files for peerconnection Blink module

Add original owners from content/renderer/media/webrtc to
the new directories in Blink.

Bug: 787254
Change-Id: I8981c3e171f47191223bc16872d7ba85fb635b2d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860027
Auto-Submit: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Armando Miraglia <armax@chromium.org>
Commit-Queue: Armando Miraglia <armax@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705619}

third_party/blink/renderer/modules/peerconnection/OWNERS

 guidou@chromium.org
 hbos@chromium.org
 orphis@chromium.org
+sergeyu@chromium.org
 steveanton@chromium.org
 tommi@chromium.org
 

third_party/blink/renderer/platform/peerconnection/OWNERS

 file://third_party/blink/renderer/modules/peerconnection/OWNERS
 
+per-file rtc_video_*=file://media/gpu/OWNERS
+
 # COMPONENT: Blink>WebRTC