[Cast] Add myself as a backup OWNER for Cast.

Add myself as a backup OWNER to miu@ for features related to Cast, to review
changes in case miu@ is OOO.

Change-Id: Id44fa744f70db2843385b06c58457fbbf5725f1d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1867206Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Tommi <tommi@chromium.org>
Commit-Queue: Tommi <tommi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707764}

chrome/browser/extensions/api/cast_streaming/OWNERS

 miu@chromium.org
+mfoltz@chromium.org
 
 # COMPONENT: Internals>Cast>Streaming

chrome/browser/extensions/api/tab_capture/OWNERS

 miu@chromium.org
+mfoltz@chromium.org
 
 # COMPONENT: Blink>GetUserMedia>Tab

chrome/browser/media/OWNERS

@@ -4,6 +4,7 @@ tommi@chromium.org
 
 # For Cast-related changes.
 per-file cast_*=miu@chromium.org
+per-file cast_*=mfoltz@chromium.org
 
 # For Media Engagement
 per-file media_engagement*=beccahughes@chromium.org

chrome/renderer/media/OWNERS

@@ -4,6 +4,7 @@ tommi@chromium.org
 
 # For Cast-related changes.
 per-file cast_*=miu@chromium.org
+per-file cast_*=mfoltz@chromium.org
 
 # FlashEmbedRewrite
 per-file flash_embed_rewrite*=mlamouri@chromium.org

components/mirroring/OWNERS

 miu@chromium.org
+mfoltz@chromium.org
 
 # COMPONENT: Internals>Cast>Streaming

media/cast/OWNERS

 miu@chromium.org
+mfoltz@chromium.org
 
 # COMPONENT: Internals>Cast>Streaming

media/remoting/OWNERS

 erickung@chromium.org
 miu@chromium.org
+mfoltz@chromium.org
 
 # COMPONENT: Internals>Cast>Streaming