[Media Router] First Run Flow WebUI and strings.

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 79808ce9d0c5c4e2928d672371f8032e18afbcba..282f3232130e970712e25a8d1bd8a6cc0e32e1da 100644
--- a/chrome/app/media_router_strings.grdp
+++ b/chrome/app/media_router_strings.grdp
@@ -48,6 +48,17 @@
    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