Roll src/third_party/leveldatabase 7306ef85..a7bff697b (4 commits).

* Deleted redundant null ptr check prior to delete.
* Fixes a bug encountered when reading records from leveldb files
  that have been split, as in a [] input task split.
* Change std::uint64_t to uint64_t (#354).
* Fix LevelDB build when asserts are enabled in release builds. (#367).

BUG=603166

Review URL: https://codereview.chromium.org/1878943014

Cr-Commit-Position: refs/heads/master@{#387695}

DEPS

@@ -144,7 +144,7 @@ deps = {
     Var('chromium_git') + '/external/google-safe-browsing/testing.git' + '@' + '9d7e8064f3ca2e45891470c9b5b1dce54af6a9d6',
 
   'src/third_party/leveldatabase/src':
-    Var('chromium_git') + '/external/leveldb.git' + '@' + '7306ef856a91e462a73ff1832c1fa8771008ba36',
+    Var('chromium_git') + '/external/leveldb.git' + '@' + 'a7bff697baa062c8f6b8fb760eacf658712b611a',
 
   'src/third_party/snappy/src':
     Var('chromium_git') + '/external/snappy.git' + '@' + '762bb32f0c9d2f31ba4958c7c0933d22e80c20bf',