ntp: use web store as default mv tile instead of themes gallery

chrome/app/resources/locale_settings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <grit latest_public_release="0" current_release="1">
   <outputs>
     <output filename="grit/locale_settings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
     </output>
     <output filename="locale_settings_am.rc" type="rc_all" lang="am" />
     <output filename="locale_settings_ar.rc" type="rc_all" lang="ar" />
     <output filename="locale_settings_bg.rc" type="rc_all" lang="bg" />
     <output filename="locale_settings_bn.rc" type="rc_all" lang="bn" />
@@ skipping 433 matching lines @@
       <!-- The language dependent download view size. -->
       <message name="IDS_DOWNLOAD_BIG_PROGRESS_SIZE" use_name_for_id="true">
         52
       </message>
 
       <!-- The URL for the themes gallery. -->
       <message name="IDS_THEMES_GALLERY_URL" translateable="false">
         https://chrome.google.com/webstore?hl=[GRITLANGCODE]&amp;category=theme
       </message>
 
+      <!-- The URL for the webstore. -->
+      <message name="IDS_WEBSTORE_URL" translateable="false">
+        https://chrome.google.com/webstore?hl=[GRITLANGCODE]
+      </message>
+
       <!-- The URL for Google Chrome welcome page. This is used for the pre -->
       <!-- populated thumbnails. -->
       <message name="IDS_CHROME_WELCOME_URL" translateable="false">
         http://www.google.com/chrome/intl/[GRITLANGCODE]/welcome.html
       </message>
 
       <!-- The URL for Adobe Flash storage settings. We cannot rely on -->
       <!-- the automatic expansion of GRITLANGCODE here because Adobe does -->
       <!-- not use the language/locale code. -->
       <message name="IDS_FLASH_STORAGE_URL" use_name_for_id="true">
@@ skipping 99 matching lines @@
         </message>
       </if>
 
       <!-- The width of the default search engine dialog in characters -->
       <message name="IDS_DEFAULT_SEARCH_WIDTH_CHARS" use_name_for_id="true">
         82
       </message>
     </messages>
   </release>
 </grit>