Make helpful announcement when there's no focus

chrome/browser/resources/chromeos/chromevox/strings/chromevox_strings.grd

Index: chrome/browser/resources/chromeos/chromevox/strings/chromevox_strings.grd
diff --git a/chrome/browser/resources/chromeos/chromevox/strings/chromevox_strings.grd b/chrome/browser/resources/chromeos/chromevox/strings/chromevox_strings.grd
index f78581d54f3cfde58ed53e141a820a4d9ae6d41a..64da50f759170972be62b4e2dd54ba9f7d553cf0 100644
--- a/chrome/browser/resources/chromeos/chromevox/strings/chromevox_strings.grd
+++ b/chrome/browser/resources/chromeos/chromevox/strings/chromevox_strings.grd
@@ -2675,6 +2675,9 @@ If you're done with the tutorial, use ChromeVox to navigate to the Close button
       <message desc="Describes an audio clip that gets played for a specific event or control type. Use the default string as a guide to what the audio clip represents or conveys." name="IDS_CHROMEVOX_WRAP_EARCON_DESCRIPTION">
         Wrap from beginning to end or end to beginning inside of a page, dialog, or other container
       </message>
+      <message desc="Announced when ChromeVox has no item in focus." name="IDS_CHROMEVOX_NO_FOCUS">
+        No focus. Press Control N to open a new window.
+      </message>
     </messages>
   </release>
 </grit>