[DeviceService] Move //device/time_zone_monitor to //services/device

device/time_zone_monitor/time_zone_monitor_linux.cc

-// Copyright 2014 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 "device/time_zone_monitor/time_zone_monitor.h"
-
-#include <stddef.h>
-#include <stdlib.h>
-
-#include <memory>
-#include <vector>
-
-#include "base/bind.h"
-#include "base/files/file_path.h"
-#include "base/files/file_path_watcher.h"
-#include "base/macros.h"
-#include "base/memory/ptr_util.h"
-#include "base/memory/ref_counted.h"
-#include "base/sequenced_task_runner.h"
-#include "base/stl_util.h"
-#include "base/threading/thread_restrictions.h"
-#include "base/threading/thread_task_runner_handle.h"
-#include "build/build_config.h"
-
-#if !defined(OS_CHROMEOS)
-
-namespace device {
-
-namespace {
-class TimeZoneMonitorLinuxImpl;
-}  // namespace
-
-class TimeZoneMonitorLinux : public TimeZoneMonitor {
- public:
-  TimeZoneMonitorLinux(
-      scoped_refptr<base::SequencedTaskRunner> file_task_runner);
-  ~TimeZoneMonitorLinux() override;
-
-  void NotifyClientsFromImpl() { NotifyClients(); }
-
- private:
-  scoped_refptr<TimeZoneMonitorLinuxImpl> impl_;
-
-  DISALLOW_COPY_AND_ASSIGN(TimeZoneMonitorLinux);
-};
-
-namespace {
-
-// FilePathWatcher needs to run on the FILE thread, but TimeZoneMonitor runs
-// on the UI thread. TimeZoneMonitorLinuxImpl is the bridge between these
-// threads.
-class TimeZoneMonitorLinuxImpl
-    : public base::RefCountedThreadSafe<TimeZoneMonitorLinuxImpl> {
- public:
-  explicit TimeZoneMonitorLinuxImpl(
-      TimeZoneMonitorLinux* owner,
-      scoped_refptr<base::SequencedTaskRunner> file_task_runner)
-      : base::RefCountedThreadSafe<TimeZoneMonitorLinuxImpl>(),
-        main_task_runner_(base::ThreadTaskRunnerHandle::Get()),
-        file_task_runner_(file_task_runner),
-        owner_(owner) {
-    DCHECK(main_task_runner_->RunsTasksOnCurrentThread());
-    file_task_runner_->PostTask(
-        FROM_HERE,
-        base::Bind(&TimeZoneMonitorLinuxImpl::StartWatchingOnFileThread, this));
-  }
-
-  void StopWatching() {
-    DCHECK(main_task_runner_->RunsTasksOnCurrentThread());
-    owner_ = NULL;
-    file_task_runner_->PostTask(
-        FROM_HERE,
-        base::Bind(&TimeZoneMonitorLinuxImpl::StopWatchingOnFileThread, this));
-  }
-
- private:
-  friend class base::RefCountedThreadSafe<TimeZoneMonitorLinuxImpl>;
-
-  ~TimeZoneMonitorLinuxImpl() {
-    DCHECK(!owner_);
-  }
-
-  void StartWatchingOnFileThread() {
-    base::ThreadRestrictions::AssertIOAllowed();
-    DCHECK(file_task_runner_->RunsTasksOnCurrentThread());
-
-    // There is no true standard for where time zone information is actually
-    // stored. glibc uses /etc/localtime, uClibc uses /etc/TZ, and some older
-    // systems store the name of the time zone file within /usr/share/zoneinfo
-    // in /etc/timezone. Different libraries and custom builds may mean that
-    // still more paths are used. Just watch all three of these paths, because
-    // false positives are harmless, assuming the false positive rate is
-    // reasonable.
-    const char* const kFilesToWatch[] = {
-        "/etc/localtime", "/etc/timezone", "/etc/TZ",
-    };
-
-    for (size_t index = 0; index < arraysize(kFilesToWatch); ++index) {
-      file_path_watchers_.push_back(base::MakeUnique<base::FilePathWatcher>());
-      file_path_watchers_.back()->Watch(
-          base::FilePath(kFilesToWatch[index]), false,
-          base::Bind(&TimeZoneMonitorLinuxImpl::OnTimeZoneFileChanged, this));
-    }
-  }
-
-  void StopWatchingOnFileThread() {
-    DCHECK(file_task_runner_->RunsTasksOnCurrentThread());
-    file_path_watchers_.clear();
-  }
-
-  void OnTimeZoneFileChanged(const base::FilePath& path, bool error) {
-    DCHECK(file_task_runner_->RunsTasksOnCurrentThread());
-    main_task_runner_->PostTask(
-        FROM_HERE,
-        base::Bind(&TimeZoneMonitorLinuxImpl::OnTimeZoneFileChangedOnUIThread,
-                   this));
-  }
-
-  void OnTimeZoneFileChangedOnUIThread() {
-    DCHECK(main_task_runner_->RunsTasksOnCurrentThread());
-    if (owner_) {
-      owner_->NotifyClientsFromImpl();
-    }
-  }
-
-  std::vector<std::unique_ptr<base::FilePathWatcher>> file_path_watchers_;
-
-  scoped_refptr<base::SequencedTaskRunner> main_task_runner_;
-  scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
-  TimeZoneMonitorLinux* owner_;
-
-  DISALLOW_COPY_AND_ASSIGN(TimeZoneMonitorLinuxImpl);
-};
-
-}  // namespace
-
-TimeZoneMonitorLinux::TimeZoneMonitorLinux(
-    scoped_refptr<base::SequencedTaskRunner> file_task_runner)
-    : TimeZoneMonitor(), impl_() {
-  // If the TZ environment variable is set, its value specifies the time zone
-  // specification, and it's pointless to monitor any files in /etc for
-  // changes because such changes would have no effect on the TZ environment
-  // variable and thus the interpretation of the local time zone in the
-  // or renderer processes.
-  //
-  // The system-specific format for the TZ environment variable beginning with
-  // a colon is implemented by glibc as the path to a time zone data file, and
-  // it would be possible to monitor this file for changes if a TZ variable of
-  // this format was encountered, but this is not necessary: when loading a
-  // time zone specification in this way, glibc does not reload the file when
-  // it changes, so it's pointless to respond to a notification that it has
-  // changed.
-  if (!getenv("TZ")) {
-    impl_ = new TimeZoneMonitorLinuxImpl(this, file_task_runner);
-  }
-}
-
-TimeZoneMonitorLinux::~TimeZoneMonitorLinux() {
-  if (impl_.get()) {
-    impl_->StopWatching();
-  }
-}
-
-// static
-std::unique_ptr<TimeZoneMonitor> TimeZoneMonitor::Create(
-    scoped_refptr<base::SequencedTaskRunner> file_task_runner) {
-  return std::unique_ptr<TimeZoneMonitor>(
-      new TimeZoneMonitorLinux(file_task_runner));
-}
-
-}  // namespace device
-
-#endif  // !OS_CHROMEOS