Add indexeddb-use-leveldb to about:flags.

chrome/app/generated_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definitions of resources that will be translated for each
 locale. OS values are passed through from Python's sys.platform:
 
   win32 - Windows
   darwin - Mac
   linux2 - Linux (both Views and GTK+)
 
@@ skipping 4246 matching lines @@
       </message>
       <message name="IDS_FLAGS_MULTI_PROFILES_DESCRIPTION" desc="Description for the flag to enable multiprofile support">
         Associates every browser window with a profile, and adds a profile switcher in the upper right corner. Every profile has its own bookmarks, extensions, apps, etc.
       </message>
       <message name="IDS_FLAGS_RESTRICT_INSTANT_TO_SEARCH_NAME" desc="Title for the flag to restrict Instant to search">
         Restrict Instant To Search
       </message>
       <message name="IDS_FLAGS_RESTRICT_INSTANT_TO_SEARCH_DESCRIPTION" desc="Description for the flag to restrict Instant to search">
         Restrict Instant to loading only search pages.
       </message>
+      <message name="IDS_FLAGS_INDEXEDDB_USE_LEVELDB_NAME" desc="Title for the flag to use the LevelDB back-end for IndexedDB">
+        IndexedDB use LevelDB.
+      </message>
+      <message name="IDS_FLAGS_INDEXEDDB_USE_LEVELDB_DESCRIPTION" desc="Description for the flag to use the LevelDB back-end for IndexedDB">
+        Enable the experimental LevelDB back-end for IndexedDB.
+      </message>
 
       <!-- Crashes -->
       <message name="IDS_CRASHES_TITLE" desc="Title for the chrome://crashes page.">
         Crashes
       </message>
       <message name="IDS_CRASHES_CRASH_COUNT_BANNER_FORMAT" desc="Format for crash count banner on chrome://crashes">
         Crashes (<ph name="CRASH_COUNT">$1<ex>3</ex></ph>)
       </message>
       <message name="IDS_CRASHES_CRASH_HEADER_FORMAT" desc="Format for crash entry headings on chrome://crashes">
         Crash ID <ph name="CRASH_ID">$1<ex>8fa95dbb6f2ec862</ex></ph>
@@ skipping 8129 matching lines @@
     </includes>
     <structures fallback_to_english="true">
       <structure name="IDD_CHROME_FRAME_FIND_DIALOG" file="cf_resources.rc" type="dialog" >
       </structure>
       <structure name="IDD_CHROME_FRAME_READY_PROMPT" file="cf_resources.rc" type="dialog" >
       </structure>
     </structures>
 
   </release>
 </grit>