Lower the I/O priority of the installer when resonable.

chrome/installer/setup/setup_util.cc

 // Copyright (c) 2012 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.
 //
 // This file declares util functions for setup project.
 
 #include "chrome/installer/setup/setup_util.h"
 
 #include <windows.h>
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/process_util.h"
 #include "base/string_util.h"
 #include "base/version.h"
+#include "base/win/windows_version.h"
 #include "chrome/installer/util/copy_tree_work_item.h"
 #include "chrome/installer/util/installation_state.h"
 #include "chrome/installer/util/installer_state.h"
 #include "chrome/installer/util/master_preferences.h"
 #include "chrome/installer/util/util_constants.h"
 #include "chrome/installer/util/work_item.h"
 #include "courgette/courgette.h"
 #include "third_party/bspatch/mbspatch.h"
 
 namespace installer {
@@ skipping 278 matching lines @@
       is_affected = is_uninstall || !product->HasOption(kOptionReadyMode);
     } else {
       is_affected = true;
     }
   }
 
   // Decide among {(1),(2),(3),(4)}.
   return is_affected ? !is_uninstall : is_present;
 }
 
+bool AdjustProcessPriority() {
+  if (base::win::GetVersion() >= base::win::VERSION_VISTA) {
+    DWORD priority_class = ::GetPriorityClass(::GetCurrentProcess());
+    if (priority_class == 0) {
+      PLOG(WARNING) << "Failed to get the process's priority class.";
+    } else if (priority_class == BELOW_NORMAL_PRIORITY_CLASS ||
+               priority_class == IDLE_PRIORITY_CLASS) {
+      BOOL result = ::SetPriorityClass(::GetCurrentProcess(),
+                                       PROCESS_MODE_BACKGROUND_BEGIN);
+      PLOG_IF(WARNING, !result) << "Failed to enter background mode.";
+      return !!result;
+    }
+  }
+  return false;
+}
+
 ScopedTokenPrivilege::ScopedTokenPrivilege(const wchar_t* privilege_name)
     : is_enabled_(false) {
   if (!::OpenProcessToken(::GetCurrentProcess(),
                           TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
                           token_.Receive())) {
     return;
   }
 
   LUID privilege_luid;
   if (!::LookupPrivilegeValue(NULL, privilege_name, &privilege_luid)) {
@@ skipping 19 matching lines @@
 }
 
 ScopedTokenPrivilege::~ScopedTokenPrivilege() {
   if (is_enabled_ && previous_privileges_.PrivilegeCount != 0) {
     ::AdjustTokenPrivileges(token_, FALSE, &previous_privileges_,
                             sizeof(TOKEN_PRIVILEGES), NULL, NULL);
   }
 }
 
 }  // namespace installer