Clarify accessibility string for bookmark menu item.

chrome/android/java/strings/android_chrome_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <grit current_release="1" latest_public_release="0">
   <outputs>
     <output filename="values-am/android_chrome_strings.xml" lang="am" type="android" />
     <output filename="values-ar/android_chrome_strings.xml" lang="ar" type="android" />
     <output filename="values-bg/android_chrome_strings.xml" lang="bg" type="android" />
     <output filename="values-ca/android_chrome_strings.xml" lang="ca" type="android" />
     <output filename="values-cs/android_chrome_strings.xml" lang="cs" type="android" />
     <output filename="values-da/android_chrome_strings.xml" lang="da" type="android" />
     <output filename="values-de/android_chrome_strings.xml" lang="de" type="android" />
@@ skipping 236 matching lines @@
       <message name="IDS_SHARE_LINK_CHOOSER_TITLE" desc="title for the share dialog when sharing the current address [CHAR-LIMIT=27]">
         Share via
       </message>
       <message name="IDS_ACCESSIBILITY_MENU_SHARE_VIA" desc="Content description share current page via the most recently used application menu item">
         Share via <ph name="APPLICATION">%s<ex>Gmail</ex></ph>
       </message>
       <message name="IDS_ERROR_PRINTING_FAILED" desc="Generic error message shown when Chrome fails to print the current page for some reason.">
         There was a problem printing the page. Please try again.
       </message>
       <message name="IDS_ACCESSIBILITY_MENU_BOOKMARK" desc="Content description for the bookmark button when the page is not currently bookmarked.">
-        Bookmark page
+        Bookmark this page
       </message>
       <message name="IDS_ACCESSIBILITY_MENU_FORWARD" desc="Content description for the forward navigation button.">
         Go forward
       </message>
       <message name="IDS_ACCESSIBILITY_MENU_BACK" desc="Content description for the backard navigation button.">
         Go back
       </message>
       <!-- ContextMenu -->
       <message name="IDS_CONTEXTMENU_OPEN_IN_NEW_TAB" desc="Context sensitive menu item to open the selected link in a new tab. [CHAR-LIMIT=30]">
         Open in new tab
@@ skipping 114 matching lines @@
       <message name="IDS_DATA_REDUCTION_INFOBAR_TEXT" desc="Text to be displayed in the data reduction proxy infobar" translateable="false">
         You are part of a data reduction proxy field trial.
       </message>
       <message name="IDS_DATA_REDUCTION_INFOBAR_LINK_TEXT" desc="Text to be displayed in the data reduction proxy infobar link" translateable="false">
         Settings
       </message>
 
     </messages>
   </release>
 </grit>