[Media Router] First Run Flow WebUI and strings.

chrome/app/media_router_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Media Router-specific strings (included from generated_resources.grd). -->
 <grit-part>
   <!-- General -->
   <message name="IDS_MEDIA_ROUTER_TITLE" desc="Title of a dialog offering possible actions for Media Router, which enables users to mirror individual tabs or desktop as well as cast content to a device.">
     Media Router
   </message>
   <message name="IDS_MEDIA_ROUTER_SHARE_YOUR_SCREEN_TEXT" desc="Tooltip for the Media Router Action icon, which appears in the toolbar. The tooltip appears on mouseover of the icon.">
    Share your screen
   </message>
@@ skipping 30 matching lines @@
   <message name="IDS_MEDIA_ROUTER_HELP" desc="Title of a menu item which, on click, opens a page to the Chromecast help center.">
    Help
   </message>
   <message name="IDS_MEDIA_ROUTER_LEARN_MORE" desc="Title of a menu item which, on click, opens a page with instructions on how to cast to a Chromecast.">
    Learn more
   </message>
   <message name="IDS_MEDIA_ROUTER_REPORT_ISSUE" desc="Title of a menu item which, on click, opens a page to give feedback or report an issue with Chromecast integration.">
    Report an issue
   </message>
 
+  <!-- First Run Flow -->
+  <message name="IDS_MEDIA_ROUTER_FIRST_RUN_FLOW_TITLE" desc="Title of the first run flow, which is shown to the user the first time they use Media Router, until they acknowledge the message. This is a welcome message that introduces Media Router to the user.">
+    Welcome to the Cast experience in Chromium!
+  </message>
+  <message name="IDS_MEDIA_ROUTER_FIRST_RUN_FLOW_TEXT" desc="Text of the first run flow, which is shown to the user the first time they use Media Router. This is an introductory description of what Media Router does.">
+    You can use this feature to display content from Chromium on your TV or other devices.
+  </message>
+  <message name="IDS_MEDIA_ROUTER_FIRST_RUN_FLOW_BUTTON" desc="Acknowledge button for the first run flow, which, on click, will dismiss the first run flow and set the current profile's preference that the user has acknowledged the first run flow.">
+    Ok, got it
+  </message>
+
   <!-- Issue Actions -->
   <message name="IDS_MEDIA_ROUTER_DISMISS_BUTTON" desc="Dismiss button, which, on click, will dismiss the current issue.">
     Dismiss
   </message>
   <message name="IDS_MEDIA_ROUTER_LEARN_MORE_BUTTON" desc="Learn more button, which, on click, will open a page with more details about the current issue.">
     Learn More
   </message>
 
   <!-- Issue Messaging -->
   <message name="IDS_MEDIA_ROUTER_ISSUE_HEADER" desc="Title of the header in the dialog when there is a user action blocking issue surfaced.">
@@ skipping 15 matching lines @@
   </message>
   <message name="IDS_MEDIA_ROUTER_STOP_CASTING_BUTTON" desc="Stop casting button, which, on click, will stop the current route.">
     Stop casting
   </message>
 
   <!-- Sink List -->
   <message name="IDS_MEDIA_ROUTER_DEVICE_MISSING" desc="Link to display when no devices are found which, on click, opens a page to the Chromecast help center explaining possible reasons why no devices are detected.">
     Device missing?
   </message>
 </grit-part>