Add a policy to always show the Cast toolbar icon

chrome/app/media_router_strings.grdp

Index: chrome/app/media_router_strings.grdp
diff --git a/chrome/app/media_router_strings.grdp b/chrome/app/media_router_strings.grdp
index 80c62614e14ebac9983772d8eaac14307f0d9fe8..36a69413e6801fc12a42ab4445ad4a0590c914fc 100644
--- a/chrome/app/media_router_strings.grdp
+++ b/chrome/app/media_router_strings.grdp
@@ -73,6 +73,9 @@
   <message name="IDS_MEDIA_ROUTER_MANAGE_DEVICES" desc="Title of a menu item which, on click, opens a page that allows the user to manage Cast devices: view, reboot, reset, and manage settings of available Cast devices, or set up new Cast devices.">
    Manage Cast devices
   </message>
+  <message name="IDS_MEDIA_ROUTER_SHOWN_BY_POLICY" desc="Title of a menu item, which indicates that the Media Router action icon was added to the toolbar by the policy enabled by the user's administrator.">
+   Added by your administrator
+  </message>
 
   <!-- First Run Flow -->
   <message name="IDS_MEDIA_ROUTER_FIRST_RUN_FLOW_CLOUD_PREF_TEXT" desc="Text of the cloud services preferences text in the first run flow, which is shown to the user if they are currently signed in and have enabled sync.">