Show "Update Chrome OS" in the wrench menu, when the update image is ready.

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 dbc81aa16936db0b1a582dbcc6f60130dff06f49..561b81ac08b25cfa96d2399e9ab9f1fafa24f699 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -8632,9 +8632,16 @@ Keep your key file in a safe place. You will need it to create new versions of y
     </message>
 
     <!-- Update Recommended dialog -->
-    <message name="IDS_UPDATE_RECOMMENDED" desc="The main text of the Update Recommended dialog.">
-      <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> is out of date because it hasn't been restarted in a while. An update is available and will be applied as soon as you restart.
-    </message>
+    <if expr="not pp_ifdef('chromeos')">
+      <message name="IDS_UPDATE_RECOMMENDED" desc="The main text of the Update Recommended dialog.">
+        <ph name="PRODUCT_NAME">$1<ex>Google Chrome</ex></ph> is out of date because it hasn't been restarted in a while. An update is available and will be applied as soon as you restart.
+      </message>
+    </if>
+    <if expr="pp_ifdef('chromeos')">
+      <message name="IDS_UPDATE_RECOMMENDED" desc="The main text of the Update Recommended dialog.">
+        <ph name="PRODUCT_NAME">$1<ex>Google Chrome OS</ex></ph> needs to be restarted to apply the update.
+      </message>
+    </if>
     <message name="IDS_RESTART_AND_UPDATE" desc="The button label for restarting and updating Chrome.">
       Restart
     </message>
@@ -8877,7 +8884,7 @@ Keep your key file in a safe place. You will need it to create new versions of y
         Finalizing system update&#x2026;
       </message>
       <message name="IDS_UPDATE_COMPLETED" desc="Notification for update completed">
-        System update complete. Please restart the system by pressing the power button, wait for the system to power down, then press the power button again.
+        System update complete. Please restart the system.
       </message>
       <message name="IDS_INSTALLING_UPDATE" desc="Label shown on the updates installation screen during OOBE">
         Please wait while <ph name="PRODUCT_NAME">$1<ex>Chrome OS</ex></ph> installs the latest system updates.