Shutdown button tooltip string changed for consistency.

BUG=331712
NOTRY=true

Review URL: https://codereview.chromium.org/147023003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247678 0039d316-1c4b-4281-b951-d872f2087c98

ash/ash_strings.grd

@@ -504,7 +504,7 @@ Press Shift + Alt to switch.
         <ph name="short_weekday">$1<ex>Fri</ex></ph>, <ph name="date">$2<ex>Aug 31, 2012</ex></ph>
       </message>
       <message name="IDS_ASH_STATUS_TRAY_SHUTDOWN" desc="The accessible text for the shutdown button.">
-        Shutdown
+        Shut down
       </message>
       <message name="IDS_ASH_STATUS_TRAY_REMAINING_SESSION_TIME" desc="The time remaining until the end of the session. Shown if the session length is limited.">
         <ph name="hours">$1<ex>01</ex></ph>:<ph name="minutes">$2<ex>35</ex></ph>:<ph name="seconds">$3<ex>12</ex></ph>