leveldb: Remove base::Feature LevelDBFileHandleEviction.

The feature has been on-by-default for quite some time.

Bug: 1080597
Change-Id: Iecc4f9d69ff465a29c3e9dccf839165e56121b0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2535875
Commit-Queue: enne <enne@chromium.org>
Reviewed-by: enne <enne@chromium.org>
Auto-Submit: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827625}

third_party/leveldatabase/env_chromium.cc

@@ -10,7 +10,6 @@
 
 #include "base/bind.h"
 #include "base/check_op.h"
-#include "base/feature_list.h"
 #include "base/files/file_util.h"
 #include "base/format_macros.h"
 #include "base/macros.h"
@@ -50,9 +49,6 @@ using leveldb::FileLock;
 using leveldb::Slice;
 using leveldb::Status;
 
-const base::Feature kLevelDBFileHandleEviction{
-    "LevelDBFileHandleEviction", base::FEATURE_ENABLED_BY_DEFAULT};
-
 namespace leveldb_env {
 namespace {
 
@@ -707,8 +703,7 @@ ChromiumEnv::ChromiumEnv(const std::string& name,
   DCHECK(filesystem_);
 
   size_t max_open_files = base::GetMaxFds();
-  if (base::FeatureList::IsEnabled(kLevelDBFileHandleEviction) &&
-      max_open_files < kFileLimitToDisableEviction) {
+  if (max_open_files < kFileLimitToDisableEviction) {
     file_cache_.reset(
         leveldb::NewLRUCache(GetLevelDBFileLimit(max_open_files)));
   }