Enable openscreen for target_os="chromeos".

Bug: None
Change-Id: Icd607790fb69a12f1355f80c2710a309a1746dc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2643422
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846387}

chrome/browser/media/router/features.gni

@@ -8,5 +8,7 @@ declare_args() {
   # Exclude openscreen in NaCl, since there is no packet support
   # in that build configuration. Once NaCl goes away, this check should be
   # removed.
-  enable_openscreen = !is_nacl && (target_os == "linux" || target_os == "mac")
+  enable_openscreen =
+      !is_nacl &&
+      (target_os == "linux" || target_os == "chromeos" || target_os == "mac")
 }