src/content/child/child_thread.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/child/child_thread.h"
   6
   7 #include <signal.h>
   8
   9 #include <string>
  10
  11 #include "base/allocator/allocator_extension.h"
  12 #include "base/base_switches.h"
  13 #include "base/basictypes.h"
  14 #include "base/command_line.h"
  15 #include "base/debug/leak_annotations.h"
  16 #include "base/lazy_instance.h"
  17 #include "base/logging.h"
  18 #include "base/message_loop/message_loop.h"
  19 #include "base/message_loop/timer_slack.h"
  20 #include "base/process/kill.h"
  21 #include "base/process/process_handle.h"
  22 #include "base/strings/string_number_conversions.h"
  23 #include "base/strings/string_util.h"
  24 #include "base/synchronization/condition_variable.h"
  25 #include "base/synchronization/lock.h"
  26 #include "base/threading/thread_local.h"
  27 #include "base/tracked_objects.h"
  28 #include "components/tracing/child_trace_message_filter.h"
  29 #include "content/child/child_histogram_message_filter.h"
  30 #include "content/child/child_process.h"
  31 #include "content/child/child_resource_message_filter.h"
  32 #include "content/child/child_shared_bitmap_manager.h"
  33 #include "content/child/fileapi/file_system_dispatcher.h"
  34 #include "content/child/fileapi/webfilesystem_impl.h"
  35 #include "content/child/mojo/mojo_application.h"
  36 #include "content/child/power_monitor_broadcast_source.h"
  37 #include "content/child/quota_dispatcher.h"
  38 #include "content/child/quota_message_filter.h"
  39 #include "content/child/resource_dispatcher.h"
  40 #include "content/child/service_worker/service_worker_dispatcher.h"
  41 #include "content/child/service_worker/service_worker_message_filter.h"
  42 #include "content/child/socket_stream_dispatcher.h"
  43 #include "content/child/thread_safe_sender.h"
  44 #include "content/child/websocket_dispatcher.h"
  45 #include "content/common/child_process_messages.h"
  46 #include "content/public/common/content_switches.h"
  47 #include "ipc/ipc_logging.h"
  48 #include "ipc/ipc_switches.h"
  49 #include "ipc/ipc_sync_channel.h"
  50 #include "ipc/ipc_sync_message_filter.h"
  51
  52 #if defined(OS_WIN)
  53 #include "content/common/handle_enumerator_win.h"
  54 #endif
  55
  56 #if defined(TCMALLOC_TRACE_MEMORY_SUPPORTED)
  57 #include "third_party/tcmalloc/chromium/src/gperftools/heap-profiler.h"
  58 #endif
  59
  60 using tracked_objects::ThreadData;
  61
  62 namespace content {
  63 namespace {
  64
  65 // How long to wait for a connection to the browser process before giving up.
  66 const int kConnectionTimeoutS = 15;
  67
  68 base::LazyInstance<base::ThreadLocalPointer<ChildThread> > g_lazy_tls =
  69     LAZY_INSTANCE_INITIALIZER;
  70
  71 // This isn't needed on Windows because there the sandbox's job object
  72 // terminates child processes automatically. For unsandboxed processes (i.e.
  73 // plugins), PluginThread has EnsureTerminateMessageFilter.
  74 #if defined(OS_POSIX)
  75
  76 // TODO(earthdok): Re-enable on CrOS http://crbug.com/360622
  77 #if (defined(ADDRESS_SANITIZER) || defined(LEAK_SANITIZER) || \
  78     defined(THREAD_SANITIZER)) && !defined(OS_CHROMEOS)
  79 // A thread delegate that waits for |duration| and then exits the process with
  80 // _exit(0).
  81 class WaitAndExitDelegate : public base::PlatformThread::Delegate {
  82  public:
  83   explicit WaitAndExitDelegate(base::TimeDelta duration)
  84       : duration_(duration) {}
  85   virtual ~WaitAndExitDelegate() OVERRIDE {}
  86
  87   virtual void ThreadMain() OVERRIDE {
  88     base::PlatformThread::Sleep(duration_);
  89     _exit(0);
  90   }
  91
  92  private:
  93   const base::TimeDelta duration_;
  94   DISALLOW_COPY_AND_ASSIGN(WaitAndExitDelegate);
  95 };
  96
  97 bool CreateWaitAndExitThread(base::TimeDelta duration) {
  98   scoped_ptr<WaitAndExitDelegate> delegate(new WaitAndExitDelegate(duration));
  99
 100   const bool thread_created =
 101       base::PlatformThread::CreateNonJoinable(0, delegate.get());
 102   if (!thread_created)
 103     return false;
 104
 105   // A non joinable thread has been created. The thread will either terminate
 106   // the process or will be terminated by the process. Therefore, keep the
 107   // delegate object alive for the lifetime of the process.
 108   WaitAndExitDelegate* leaking_delegate = delegate.release();
 109   ANNOTATE_LEAKING_OBJECT_PTR(leaking_delegate);
 110   ignore_result(leaking_delegate);
 111   return true;
 112 }
 113 #endif
 114
 115 class SuicideOnChannelErrorFilter : public IPC::MessageFilter {
 116  public:
 117   // IPC::MessageFilter
 118   virtual void OnChannelError() OVERRIDE {
 119     // For renderer/worker processes:
 120     // On POSIX, at least, one can install an unload handler which loops
 121     // forever and leave behind a renderer process which eats 100% CPU forever.
 122     //
 123     // This is because the terminate signals (ViewMsg_ShouldClose and the error
 124     // from the IPC sender) are routed to the main message loop but never
 125     // processed (because that message loop is stuck in V8).
 126     //
 127     // One could make the browser SIGKILL the renderers, but that leaves open a
 128     // large window where a browser failure (or a user, manually terminating
 129     // the browser because "it's stuck") will leave behind a process eating all
 130     // the CPU.
 131     //
 132     // So, we install a filter on the sender so that we can process this event
 133     // here and kill the process.
 134     // TODO(earthdok): Re-enable on CrOS http://crbug.com/360622
 135 #if (defined(ADDRESS_SANITIZER) || defined(LEAK_SANITIZER) || \
 136     defined(THREAD_SANITIZER)) && !defined(OS_CHROMEOS)
 137     // Some sanitizer tools rely on exit handlers (e.g. to run leak detection,
 138     // or dump code coverage data to disk). Instead of exiting the process
 139     // immediately, we give it 60 seconds to run exit handlers.
 140     CHECK(CreateWaitAndExitThread(base::TimeDelta::FromSeconds(60)));
 141 #if defined(LEAK_SANITIZER)
 142     // Invoke LeakSanitizer early to avoid detecting shutdown-only leaks. If
 143     // leaks are found, the process will exit here.
 144     __lsan_do_leak_check();
 145 #endif
 146 #else
 147     _exit(0);
 148 #endif
 149   }
 150
 151  protected:
 152   virtual ~SuicideOnChannelErrorFilter() {}
 153 };
 154
 155 #endif  // OS(POSIX)
 156
 157 #if defined(OS_ANDROID)
 158 ChildThread* g_child_thread = NULL;
 159
 160 // A lock protects g_child_thread.
 161 base::LazyInstance<base::Lock> g_lazy_child_thread_lock =
 162     LAZY_INSTANCE_INITIALIZER;
 163
 164 // base::ConditionVariable has an explicit constructor that takes
 165 // a base::Lock pointer as parameter. The base::DefaultLazyInstanceTraits
 166 // doesn't handle the case. Thus, we need our own class here.
 167 struct CondVarLazyInstanceTraits {
 168   static const bool kRegisterOnExit = true;
 169 #ifndef NDEBUG
 170   static const bool kAllowedToAccessOnNonjoinableThread = false;
 171 #endif
 172
 173   static base::ConditionVariable* New(void* instance) {
 174     return new (instance) base::ConditionVariable(
 175         g_lazy_child_thread_lock.Pointer());
 176   }
 177   static void Delete(base::ConditionVariable* instance) {
 178     instance->~ConditionVariable();
 179   }
 180 };
 181
 182 // A condition variable that synchronize threads initializing and waiting
 183 // for g_child_thread.
 184 base::LazyInstance<base::ConditionVariable, CondVarLazyInstanceTraits>
 185     g_lazy_child_thread_cv = LAZY_INSTANCE_INITIALIZER;
 186
 187 void QuitMainThreadMessageLoop() {
 188   base::MessageLoop::current()->Quit();
 189 }
 190
 191 #endif
 192
 193 }  // namespace
 194
 195 ChildThread::ChildThreadMessageRouter::ChildThreadMessageRouter(
 196     IPC::Sender* sender)
 197     : sender_(sender) {}
 198
 199 bool ChildThread::ChildThreadMessageRouter::Send(IPC::Message* msg) {
 200   return sender_->Send(msg);
 201 }
 202
 203 ChildThread::ChildThread()
 204     : router_(this),
 205       channel_connected_factory_(this),
 206       in_browser_process_(false) {
 207   channel_name_ = CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 208       switches::kProcessChannelID);
 209   Init();
 210 }
 211
 212 ChildThread::ChildThread(const std::string& channel_name)
 213     : channel_name_(channel_name),
 214       router_(this),
 215       channel_connected_factory_(this),
 216       in_browser_process_(true) {
 217   Init();
 218 }
 219
 220 void ChildThread::Init() {
 221   g_lazy_tls.Pointer()->Set(this);
 222   on_channel_error_called_ = false;
 223   message_loop_ = base::MessageLoop::current();
 224 #ifdef IPC_MESSAGE_LOG_ENABLED
 225   // We must make sure to instantiate the IPC Logger *before* we create the
 226   // channel, otherwise we can get a callback on the IO thread which creates
 227   // the logger, and the logger does not like being created on the IO thread.
 228   IPC::Logging::GetInstance();
 229 #endif
 230   channel_ =
 231       IPC::SyncChannel::Create(channel_name_,
 232                                IPC::Channel::MODE_CLIENT,
 233                                this,
 234                                ChildProcess::current()->io_message_loop_proxy(),
 235                                true,
 236                                ChildProcess::current()->GetShutDownEvent());
 237 #ifdef IPC_MESSAGE_LOG_ENABLED
 238   if (!in_browser_process_)
 239     IPC::Logging::GetInstance()->SetIPCSender(this);
 240 #endif
 241
 242   mojo_application_.reset(new MojoApplication(this));
 243
 244   sync_message_filter_ =
 245       new IPC::SyncMessageFilter(ChildProcess::current()->GetShutDownEvent());
 246   thread_safe_sender_ = new ThreadSafeSender(
 247       base::MessageLoopProxy::current().get(), sync_message_filter_.get());
 248
 249   resource_dispatcher_.reset(new ResourceDispatcher(this));
 250   socket_stream_dispatcher_.reset(new SocketStreamDispatcher());
 251   websocket_dispatcher_.reset(new WebSocketDispatcher);
 252   file_system_dispatcher_.reset(new FileSystemDispatcher());
 253
 254   histogram_message_filter_ = new ChildHistogramMessageFilter();
 255   resource_message_filter_ =
 256       new ChildResourceMessageFilter(resource_dispatcher());
 257
 258   service_worker_message_filter_ =
 259       new ServiceWorkerMessageFilter(thread_safe_sender_.get());
 260   service_worker_dispatcher_.reset(
 261       new ServiceWorkerDispatcher(thread_safe_sender_.get()));
 262
 263   quota_message_filter_ =
 264       new QuotaMessageFilter(thread_safe_sender_.get());
 265   quota_dispatcher_.reset(new QuotaDispatcher(thread_safe_sender_.get(),
 266                                               quota_message_filter_.get()));
 267
 268   channel_->AddFilter(histogram_message_filter_.get());
 269   channel_->AddFilter(sync_message_filter_.get());
 270   channel_->AddFilter(resource_message_filter_.get());
 271   channel_->AddFilter(quota_message_filter_->GetFilter());
 272   channel_->AddFilter(service_worker_message_filter_->GetFilter());
 273
 274   if (!CommandLine::ForCurrentProcess()->HasSwitch(switches::kSingleProcess)) {
 275     // In single process mode, browser-side tracing will cover the whole
 276     // process including renderers.
 277     channel_->AddFilter(new tracing::ChildTraceMessageFilter(
 278         ChildProcess::current()->io_message_loop_proxy()));
 279   }
 280
 281   // In single process mode we may already have a power monitor
 282   if (!base::PowerMonitor::Get()) {
 283     scoped_ptr<PowerMonitorBroadcastSource> power_monitor_source(
 284       new PowerMonitorBroadcastSource());
 285     channel_->AddFilter(power_monitor_source->GetMessageFilter());
 286
 287     power_monitor_.reset(new base::PowerMonitor(
 288         power_monitor_source.PassAs<base::PowerMonitorSource>()));
 289   }
 290
 291 #if defined(OS_POSIX)
 292   // Check that --process-type is specified so we don't do this in unit tests
 293   // and single-process mode.
 294   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kProcessType))
 295     channel_->AddFilter(new SuicideOnChannelErrorFilter());
 296 #endif
 297
 298   int connection_timeout = kConnectionTimeoutS;
 299   std::string connection_override =
 300       CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 301           switches::kIPCConnectionTimeout);
 302   if (!connection_override.empty()) {
 303     int temp;
 304     if (base::StringToInt(connection_override, &temp))
 305       connection_timeout = temp;
 306   }
 307
 308   base::MessageLoop::current()->PostDelayedTask(
 309       FROM_HERE,
 310       base::Bind(&ChildThread::EnsureConnected,
 311                  channel_connected_factory_.GetWeakPtr()),
 312       base::TimeDelta::FromSeconds(connection_timeout));
 313
 314 #if defined(OS_ANDROID)
 315   {
 316     base::AutoLock lock(g_lazy_child_thread_lock.Get());
 317     g_child_thread = this;
 318   }
 319   // Signalling without locking is fine here because only
 320   // one thread can wait on the condition variable.
 321   g_lazy_child_thread_cv.Get().Signal();
 322 #endif
 323
 324 #if defined(TCMALLOC_TRACE_MEMORY_SUPPORTED)
 325   trace_memory_controller_.reset(new base::debug::TraceMemoryController(
 326       message_loop_->message_loop_proxy(),
 327       ::HeapProfilerWithPseudoStackStart,
 328       ::HeapProfilerStop,
 329       ::GetHeapProfile));
 330 #endif
 331
 332   shared_bitmap_manager_.reset(
 333       new ChildSharedBitmapManager(thread_safe_sender()));
 334 }
 335
 336 ChildThread::~ChildThread() {
 337 #ifdef IPC_MESSAGE_LOG_ENABLED
 338   IPC::Logging::GetInstance()->SetIPCSender(NULL);
 339 #endif
 340
 341   channel_->RemoveFilter(histogram_message_filter_.get());
 342   channel_->RemoveFilter(sync_message_filter_.get());
 343
 344   // The ChannelProxy object caches a pointer to the IPC thread, so need to
 345   // reset it as it's not guaranteed to outlive this object.
 346   // NOTE: this also has the side-effect of not closing the main IPC channel to
 347   // the browser process.  This is needed because this is the signal that the
 348   // browser uses to know that this process has died, so we need it to be alive
 349   // until this process is shut down, and the OS closes the handle
 350   // automatically.  We used to watch the object handle on Windows to do this,
 351   // but it wasn't possible to do so on POSIX.
 352   channel_->ClearIPCTaskRunner();
 353   g_lazy_tls.Pointer()->Set(NULL);
 354 }
 355
 356 void ChildThread::Shutdown() {
 357   // Delete objects that hold references to blink so derived classes can
 358   // safely shutdown blink in their Shutdown implementation.
 359   file_system_dispatcher_.reset();
 360   quota_dispatcher_.reset();
 361   WebFileSystemImpl::DeleteThreadSpecificInstance();
 362 }
 363
 364 void ChildThread::OnChannelConnected(int32 peer_pid) {
 365   channel_connected_factory_.InvalidateWeakPtrs();
 366 }
 367
 368 void ChildThread::OnChannelError() {
 369   set_on_channel_error_called(true);
 370   base::MessageLoop::current()->Quit();
 371 }
 372
 373 void ChildThread::ConnectToService(
 374     const mojo::String& service_url,
 375     const mojo::String& service_name,
 376     mojo::ScopedMessagePipeHandle message_pipe,
 377     const mojo::String& requestor_url) {
 378   // By default, we don't expect incoming connections.
 379   NOTREACHED();
 380 }
 381
 382 bool ChildThread::Send(IPC::Message* msg) {
 383   DCHECK(base::MessageLoop::current() == message_loop());
 384   if (!channel_) {
 385     delete msg;
 386     return false;
 387   }
 388
 389   return channel_->Send(msg);
 390 }
 391
 392 MessageRouter* ChildThread::GetRouter() {
 393   DCHECK(base::MessageLoop::current() == message_loop());
 394   return &router_;
 395 }
 396
 397 base::SharedMemory* ChildThread::AllocateSharedMemory(size_t buf_size) {
 398   return AllocateSharedMemory(buf_size, this);
 399 }
 400
 401 // static
 402 base::SharedMemory* ChildThread::AllocateSharedMemory(
 403     size_t buf_size,
 404     IPC::Sender* sender) {
 405   scoped_ptr<base::SharedMemory> shared_buf;
 406 #if defined(OS_WIN)
 407   shared_buf.reset(new base::SharedMemory);
 408   if (!shared_buf->CreateAndMapAnonymous(buf_size)) {
 409     NOTREACHED();
 410     return NULL;
 411   }
 412 #else
 413   // On POSIX, we need to ask the browser to create the shared memory for us,
 414   // since this is blocked by the sandbox.
 415   base::SharedMemoryHandle shared_mem_handle;
 416   if (sender->Send(new ChildProcessHostMsg_SyncAllocateSharedMemory(
 417                            buf_size, &shared_mem_handle))) {
 418     if (base::SharedMemory::IsHandleValid(shared_mem_handle)) {
 419       shared_buf.reset(new base::SharedMemory(shared_mem_handle, false));
 420       if (!shared_buf->Map(buf_size)) {
 421         NOTREACHED() << "Map failed";
 422         return NULL;
 423       }
 424     } else {
 425       NOTREACHED() << "Browser failed to allocate shared memory";
 426       return NULL;
 427     }
 428   } else {
 429     NOTREACHED() << "Browser allocation request message failed";
 430     return NULL;
 431   }
 432 #endif
 433   return shared_buf.release();
 434 }
 435
 436 bool ChildThread::OnMessageReceived(const IPC::Message& msg) {
 437   if (mojo_application_->OnMessageReceived(msg))
 438     return true;
 439
 440   // Resource responses are sent to the resource dispatcher.
 441   if (resource_dispatcher_->OnMessageReceived(msg))
 442     return true;
 443   if (socket_stream_dispatcher_->OnMessageReceived(msg))
 444     return true;
 445   if (websocket_dispatcher_->OnMessageReceived(msg))
 446     return true;
 447   if (file_system_dispatcher_->OnMessageReceived(msg))
 448     return true;
 449
 450   bool handled = true;
 451   IPC_BEGIN_MESSAGE_MAP(ChildThread, msg)
 452     IPC_MESSAGE_HANDLER(ChildProcessMsg_Shutdown, OnShutdown)
 453 #if defined(IPC_MESSAGE_LOG_ENABLED)
 454     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetIPCLoggingEnabled,
 455                         OnSetIPCLoggingEnabled)
 456 #endif
 457     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetProfilerStatus,
 458                         OnSetProfilerStatus)
 459     IPC_MESSAGE_HANDLER(ChildProcessMsg_GetChildProfilerData,
 460                         OnGetChildProfilerData)
 461     IPC_MESSAGE_HANDLER(ChildProcessMsg_DumpHandles, OnDumpHandles)
 462     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetProcessBackgrounded,
 463                         OnProcessBackgrounded)
 464 #if defined(USE_TCMALLOC)
 465     IPC_MESSAGE_HANDLER(ChildProcessMsg_GetTcmallocStats, OnGetTcmallocStats)
 466 #endif
 467     IPC_MESSAGE_UNHANDLED(handled = false)
 468   IPC_END_MESSAGE_MAP()
 469
 470   if (handled)
 471     return true;
 472
 473   if (msg.routing_id() == MSG_ROUTING_CONTROL)
 474     return OnControlMessageReceived(msg);
 475
 476   return router_.OnMessageReceived(msg);
 477 }
 478
 479 bool ChildThread::OnControlMessageReceived(const IPC::Message& msg) {
 480   return false;
 481 }
 482
 483 void ChildThread::OnShutdown() {
 484   base::MessageLoop::current()->Quit();
 485 }
 486
 487 #if defined(IPC_MESSAGE_LOG_ENABLED)
 488 void ChildThread::OnSetIPCLoggingEnabled(bool enable) {
 489   if (enable)
 490     IPC::Logging::GetInstance()->Enable();
 491   else
 492     IPC::Logging::GetInstance()->Disable();
 493 }
 494 #endif  //  IPC_MESSAGE_LOG_ENABLED
 495
 496 void ChildThread::OnSetProfilerStatus(ThreadData::Status status) {
 497   ThreadData::InitializeAndSetTrackingStatus(status);
 498 }
 499
 500 void ChildThread::OnGetChildProfilerData(int sequence_number) {
 501   tracked_objects::ProcessDataSnapshot process_data;
 502   ThreadData::Snapshot(false, &process_data);
 503
 504   Send(new ChildProcessHostMsg_ChildProfilerData(sequence_number,
 505                                                  process_data));
 506 }
 507
 508 void ChildThread::OnDumpHandles() {
 509 #if defined(OS_WIN)
 510   scoped_refptr<HandleEnumerator> handle_enum(
 511       new HandleEnumerator(
 512           CommandLine::ForCurrentProcess()->HasSwitch(
 513               switches::kAuditAllHandles)));
 514   handle_enum->EnumerateHandles();
 515   Send(new ChildProcessHostMsg_DumpHandlesDone);
 516 #else
 517   NOTIMPLEMENTED();
 518 #endif
 519 }
 520
 521 #if defined(USE_TCMALLOC)
 522 void ChildThread::OnGetTcmallocStats() {
 523   std::string result;
 524   char buffer[1024 * 32];
 525   base::allocator::GetStats(buffer, sizeof(buffer));
 526   result.append(buffer);
 527   Send(new ChildProcessHostMsg_TcmallocStats(result));
 528 }
 529 #endif
 530
 531 ChildThread* ChildThread::current() {
 532   return g_lazy_tls.Pointer()->Get();
 533 }
 534
 535 #if defined(OS_ANDROID)
 536 // The method must NOT be called on the child thread itself.
 537 // It may block the child thread if so.
 538 void ChildThread::ShutdownThread() {
 539   DCHECK(!ChildThread::current()) <<
 540       "this method should NOT be called from child thread itself";
 541   {
 542     base::AutoLock lock(g_lazy_child_thread_lock.Get());
 543     while (!g_child_thread)
 544       g_lazy_child_thread_cv.Get().Wait();
 545   }
 546   DCHECK_NE(base::MessageLoop::current(), g_child_thread->message_loop());
 547   g_child_thread->message_loop()->PostTask(
 548       FROM_HERE, base::Bind(&QuitMainThreadMessageLoop));
 549 }
 550 #endif
 551
 552 void ChildThread::OnProcessFinalRelease() {
 553   if (on_channel_error_called_) {
 554     base::MessageLoop::current()->Quit();
 555     return;
 556   }
 557
 558   // The child process shutdown sequence is a request response based mechanism,
 559   // where we send out an initial feeler request to the child process host
 560   // instance in the browser to verify if it's ok to shutdown the child process.
 561   // The browser then sends back a response if it's ok to shutdown. This avoids
 562   // race conditions if the process refcount is 0 but there's an IPC message
 563   // inflight that would addref it.
 564   Send(new ChildProcessHostMsg_ShutdownRequest);
 565 }
 566
 567 void ChildThread::EnsureConnected() {
 568   VLOG(0) << "ChildThread::EnsureConnected()";
 569   base::KillProcess(base::GetCurrentProcessHandle(), 0, false);
 570 }
 571
 572 void ChildThread::OnProcessBackgrounded(bool background) {
 573   // Set timer slack to maximum on main thread when in background.
 574   base::TimerSlack timer_slack = base::TIMER_SLACK_NONE;
 575   if (background)
 576     timer_slack = base::TIMER_SLACK_MAXIMUM;
 577   base::MessageLoop::current()->SetTimerSlack(timer_slack);
 578
 579 #ifdef OS_WIN
 580   // Windows Vista+ has a fancy process backgrounding mode that can only be set
 581   // from within the process.
 582   base::Process::Current().SetProcessBackgrounded(background);
 583 #endif  // OS_WIN
 584 }
 585
 586 }  // namespace content