Add missing miu@ to OWNERS files for Cast Streaming, and pruning.

Removed pwestin@ and mikhal@ from OWNERS files, since they have been off
the project for over a year.

Review URL: https://codereview.chromium.org/1074573002

Cr-Commit-Position: refs/heads/master@{#324300}

chrome/browser/media/OWNERS

@@ -5,10 +5,10 @@ sergeyu@chromium.org
 tommi@chromium.org
 xhwang@chromium.org
 
+# For Cast streaming changes.
 per-file cast_*=hclam@chromium.org
 per-file cast_*=hubbe@chromium.org
-per-file cast_*=mikhal@chromium.org
-per-file cast_*=pwestin@google.com
+per-file cast_*=miu@chromium.org
 
 # For WebRTC browser tests, etc.
 per-file *webrtc*browsertest*=phoglund@chromium.org

chrome/renderer/media/OWNERS

@@ -7,7 +7,7 @@ sergeyu@chromium.org
 tommi@chromium.org
 xhwang@chromium.org
 
+# For Cast streaming changes.
 per-file cast_*=hclam@chromium.org
 per-file cast_*=hubbe@chromium.org
-per-file cast_*=mikhal@chromium.org
-per-file cast_*=pwestin@google.com
+per-file cast_*=miu@chromium.org

content/renderer/media/OWNERS

@@ -10,10 +10,10 @@ xhwang@chromium.org
 perkj@chromium.org
 tommi@chromium.org
 
+# Cast Streaming OWNERS.
 per-file cast_*=hclam@chromium.org
 per-file cast_*=hubbe@chromium.org
-per-file cast_*=mikhal@chromium.org
-per-file cast_*=pwestin@google.com
+per-file cast_*=miu@chromium.org
 
 per-file midi_*=toyoshim@chromium.org
 per-file renderer_webmidi*=toyoshim@chromium.org

media/cast/OWNERS

 hclam@chromium.org
 hubbe@chromium.org
-mikhal@chromium.org
 miu@chromium.org
-pwestin@google.com