cros: add new search box hint text for launcher

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index fbe2be209e13d6cc9b729910413716ac0ae493dc..013cfb132dd48118047eab2bb9518ae3d82cebf1 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -11143,6 +11143,9 @@ Please check your email at <ph name="ACCOUNT_EMAIL">$2<ex>jane.doe@gmail.com</ex
         <message name="IDS_SEARCH_BOX_HINT" desc="Hint text for the search box in app list window.">
           Search or type URL
         </message>
+        <message name="IDS_SEARCH_BOX_HINT_FULLSCREEN" desc="Hint text for the search box in fullscreen app list window.">
+          Search your Chromebook, apps, web...

[xiyuan, 2017/06/12 19:24:55]

Usually we use a place holder for "Chromebook" and replace it with what
ash::GetChromeOSDeviceName() returns.

e.g.

https://cs.chromium.org/chromium/src/chrome/browser/chromeos/arc/arc_auth_not...

[Qiang(Joe) Xu, 2017/06/12 21:45:31]

done

+        </message>
         <message name="IDS_SEARCH_BOX_HOTWORD_HINT" desc="Hint text for the search box in app list window when the hotword is enabled.">
           Search, or say "Ok Google"
         </message>