Broadcast NotifyTimezoneChange to all RenderProcessHosts when the system time zone changes

content/browser/time_zone_monitor.h

+// 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.
+
+#ifndef CONTENT_BROWSER_TIME_ZONE_MONITOR_H_
+#define CONTENT_BROWSER_TIME_ZONE_MONITOR_H_
+
+#include "base/basictypes.h"
+
+namespace content {
+
+// TimeZoneMonitor watches the system time zone, and notifies renderers
+// when it changes. Some renderer code caches the system time zone, so
+// this notification is necessary to inform such code that cached
+// timezone data may have become invalid. Due to sandboxing, it is not
+// possible for renderer processes to monitor for system time zone
+// changes themselves, so this must happen in the browser process.
+//
+// Sandboxing also may prevent renderer processes from reading the time
+// zone when it does change, so platforms may have to deal with this in
+// platform-specific ways:
+//  - Mac uses a sandbox hole defined in content/renderer/renderer.sb.
+//  - Linux-based platforms use ProxyLocaltimeCallToBrowser in
+//    content/zygote/zygote_main_linux.cc and HandleLocaltime in
+//    content/browser/renderer_host/sandbox_ipc_linux.cc to override
+//    localtime in renderer processes with custom code that calls
+//    localtime in the browser process via Chrome IPC.
+
+class TimeZoneMonitor {
+ public:
+  // Returns a new TimeZoneMonitor object (likely a subclass) specific to the
+  // platform.
+  static TimeZoneMonitor* Create();

[Robert Sesek, 2014/04/28 20:53:39]

I think the preference now is to return a scoped_ptr<T> from Create methods so
that the object can't ever accidentally leak.

+
+  TimeZoneMonitor();

[Robert Sesek, 2014/04/28 20:53:39]

Should the ctor be public if you have a Create method?

[Mark Mentovai, 2014/04/28 21:08:38]

rsesek wrote:
Create’s a static method from the base class. It doesn’t have access to anything
that’s not public.

[Robert Sesek, 2014/04/28 21:14:48]

Right, but is it meaningful to actually construct a TimeZoneMonitor base class?
It seems like you should restrict the public API to what people should actually
call.

+  virtual ~TimeZoneMonitor();
+
+ protected:
+  // Loop over all renderers and notify them that the system time zone may
+  // have changed.
+  void NotifyRenderers();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TimeZoneMonitor);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_TIME_ZONE_MONITOR_H_