Update from https://crrev.com/316786

net/disk_cache/simple/simple_backend_impl.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/simple/simple_backend_impl.h"
 
 #include <algorithm>
 #include <cstdlib>
 #include <functional>
 
@@ skipping 32 matching lines @@
 using base::Time;
 using base::DirectoryExists;
 using base::CreateDirectory;
 
 namespace disk_cache {
 
 namespace {
 
 // Maximum number of concurrent worker pool threads, which also is the limit
 // on concurrent IO (as we use one thread per IO request).
-const int kDefaultMaxWorkerThreads = 50;
+const size_t kMaxWorkerThreads = 5U;
 
 const char kThreadNamePrefix[] = "SimpleCache";
 
 // Maximum fraction of the cache that one entry can consume.
 const int kMaxFileRatio = 8;
 
 // A global sequenced worker pool to use for launching all tasks.
 SequencedWorkerPool* g_sequenced_worker_pool = NULL;
 
 void MaybeCreateSequencedWorkerPool() {
   if (!g_sequenced_worker_pool) {
-    int max_worker_threads = kDefaultMaxWorkerThreads;
-
-    const std::string thread_count_field_trial =
-        base::FieldTrialList::FindFullName("SimpleCacheMaxThreads");
-    if (!thread_count_field_trial.empty()) {
-      max_worker_threads =
-          std::max(1, std::atoi(thread_count_field_trial.c_str()));
-    }
-
-    g_sequenced_worker_pool = new SequencedWorkerPool(max_worker_threads,
-                                                      kThreadNamePrefix);
+    g_sequenced_worker_pool =
+        new SequencedWorkerPool(kMaxWorkerThreads, kThreadNamePrefix);
     g_sequenced_worker_pool->AddRef();  // Leak it.
   }
 }
 
 bool g_fd_limit_histogram_has_been_populated = false;
 
 void MaybeHistogramFdLimit(net::CacheType cache_type) {
   if (g_fd_limit_histogram_has_been_populated)
     return;
 
@@ skipping 646 matching lines @@
                    this));
   callback.Run(result);
 }
 
 void SimpleBackendImpl::FlushWorkerPoolForTesting() {
   if (g_sequenced_worker_pool)
     g_sequenced_worker_pool->FlushForTesting();
 }
 
 }  // namespace disk_cache