Try changing LockImpl to not have a spin count to see how it affects performance.

base/synchronization/lock_impl_win.cc

 // Copyright (c) 2011 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 "base/synchronization/lock_impl.h"
 
 namespace base {
 namespace internal {
 
 LockImpl::LockImpl() {
-  // The second parameter is the spin count, for short-held locks it avoid the
-  // contending thread from going to sleep which helps performance greatly.
-  ::InitializeCriticalSectionAndSpinCount(&native_handle_, 2000);
+  ::InitializeCriticalSection(&native_handle_);
 }
 
 LockImpl::~LockImpl() {
   ::DeleteCriticalSection(&native_handle_);
 }
 
 bool LockImpl::Try() {
   if (::TryEnterCriticalSection(&native_handle_) != FALSE) {
     return true;
   }
   return false;
 }
 
 void LockImpl::Lock() {
   ::EnterCriticalSection(&native_handle_);
 }
 
 void LockImpl::Unlock() {
   ::LeaveCriticalSection(&native_handle_);
 }
 
 }  // namespace internal
 }  // namespace base