IndexedDB: Enable leveldb log reuse on Chrome OS.

Reuse was disabled in #317499 because CrOS corruption rates were spiking and
were too close to the stable branch point to gather more history.  Re-enabling
to allow monitoring in dev/beta channels with the hope that the rise we saw on
CrOS was normal fluctuations and unrelated to this change.

BUG=460568

Review URL: https://codereview.chromium.org/1023773003

Cr-Commit-Position: refs/heads/master@{#321427}

content/browser/indexed_db/leveldb/leveldb_database.cc

@@ -103,12 +103,7 @@ static leveldb::Status OpenDB(
   options.create_if_missing = true;
   options.paranoid_checks = true;
   options.filter_policy = filter_policy->get();
-#if defined(OS_CHROMEOS)
-  // Disabled on CrOS until crbug.com/460568 is fixed.
-  options.reuse_logs = false;
-#else
   options.reuse_logs = true;
-#endif
   options.compression = leveldb::kSnappyCompression;
 
   // For info about the troubles we've run into with this parameter, see:

third_party/leveldatabase/env_chromium.cc

@@ -896,14 +896,6 @@ Status ChromiumEnv::NewWritableFile(const std::string& fname,
 
 Status ChromiumEnv::NewAppendableFile(const std::string& fname,
                                       leveldb::WritableFile** result) {
-#if defined(OS_CHROMEOS)
-  // Disabled until crbug.com/460568 is fixed. Technically this method shouldn't
-  // be called if reuse_logs is false, but a leveldb bug (fixed, but not yet in
-  // Chrome) still calls this function. Using default leveldb Env implementation
-  // to workaround this bug.
-  return Env::NewAppendableFile(fname, result);
-#endif
-
   *result = NULL;
   FilePath path = FilePath::FromUTF8Unsafe(fname);
   scoped_ptr<base::File> f(new base::File(