Roll LevelDB to r54.

DEPS

 vars = {
   # Use this googlecode_url variable only if there is an internal mirror for it.
   # If you do not know, use the full path while defining your new deps entry.
   "googlecode_url": "http://%s.googlecode.com/svn",
   "sourceforge_url": "http://%(repo)s.svn.sourceforge.net/svnroot/%(repo)s",
   "webkit_trunk": "http://svn.webkit.org/repository/webkit/trunk",
   "nacl_trunk": "http://src.chromium.org/native_client/trunk",
   "webkit_revision": "98752",
   "chromium_git": "http://git.chromium.org/git",
   "swig_revision": "69281",
@@ skipping 73 matching lines @@
     "/trunk/deps/third_party/hunspell_dictionaries@79099",
 
   "src/third_party/safe_browsing/testing":
     (Var("googlecode_url") % "google-safe-browsing") + "/trunk/testing@106",
 
   "src/third_party/cacheinvalidation/files/src/google":
     (Var("googlecode_url") % "google-cache-invalidation-api") +
     "/trunk/src/google@143",
 
   "src/third_party/leveldatabase/src":
-    (Var("googlecode_url") % "leveldb") + "/trunk@53",
+    (Var("googlecode_url") % "leveldb") + "/trunk@54",
 
   "src/third_party/snappy/src":
     (Var("googlecode_url") % "snappy") + "/trunk@37",
 
   "src/tools/grit":
     (Var("googlecode_url") % "grit-i18n") + "/trunk@6",
 
   "src/tools/gyp":
     (Var("googlecode_url") % "gyp") + "/trunk@1083",
 
@@ skipping 341 matching lines @@
     # which takes ~20s, but clang speeds up builds by more than 20s.
     "pattern": ".",
     "action": ["python", "src/tools/clang/scripts/update.py", "--mac-only"],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "src/build/gyp_chromium"],
   },
 ]