"Start Screen" string -> "Start screen"

BUG=140069
TEST= Menu entry in wrench menu in Win8/Metro is "Pin to Start screen" (i.e. uncapitalized "screen").

Review URL: https://chromiumcodereview.appspot.com/10834114

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@149674 0039d316-1c4b-4281-b951-d872f2087c98

chrome/app/generated_resources.grd

@@ -952,10 +952,10 @@ Psst! Incognito mode <ph name="SHORTCUT_KEY">$1<ex>(Ctrl+Shift+N)</ex></ph> may
           New &amp;incognito window
         </message>
         <message name="IDS_METRO_PIN_TO_START_SCREEN" desc="The text label of the Pin to start screen menu item">
-          Pin to Start Screen
+          Pin to Start screen
         </message>
         <message name="IDS_METRO_UNPIN_FROM_START_SCREEN" desc="The text label of the unpin from start screen menu item">
-          Unpin from Start Screen
+          Unpin from Start screen
         </message>
         <message name="IDS_EDIT2" desc="The text label before the cut/copy/paste buttons in the merged menu">
           Edit