Make DeviceSensorService implement MainLoop::DestructionObserver

services/device/device_service.cc

Index: services/device/device_service.cc
diff --git a/services/device/device_service.cc b/services/device/device_service.cc
index 0044460a1d9c1dd4bb4d99313ae24f2582b861bb..04287e32bd05aba7530f8ced32a575fcefb8b3ea 100644
--- a/services/device/device_service.cc
+++ b/services/device/device_service.cc
@@ -15,6 +15,8 @@
 #include "services/service_manager/public/cpp/interface_registry.h"
 
 #if defined(OS_ANDROID)
+#include "base/trace_event/trace_event.h"
+#include "device/sensors/device_sensor_service.h"
 #include "services/device/android/register_jni.h"
 #endif
 
@@ -36,7 +38,12 @@ DeviceService::DeviceService(
     scoped_refptr<base::SingleThreadTaskRunner> file_task_runner)
     : file_task_runner_(std::move(file_task_runner)) {}
 
-DeviceService::~DeviceService() {}
+DeviceService::~DeviceService() {
+#if defined(OS_ANDROID)
+  TRACE_EVENT0("shutdown", "DeviceService::Subsystem:SensorService");

[ke.he, 2017/03/08 09:19:55]

For Android platform, it is safe to shutdown in UI thread, no need to care about
whether IO thread is live or not.

[blundell, 2017/03/08 17:38:17]

Do you think that we could just use the same mechanism on Android as on other
platforms, i.e., have it observe the destruction of the message loop that it's
running on?

[ke.he, 2017/03/09 02:37:33]

For Android platform, DeviceSensorService runs in UI thread, it needs to get an
"io_task_runner" to add itself into IO MessageLoop's observer list.
DeviceSensorService is process singleton, it is created in
"DeviceSensorService::GetInstance()" when "DeviceSensorHost::StartPolling()" is
first called. so we need to pass the "io_task_runner" to DeviceSensorHost in
"RenderProcessHostImpl::AddUIThreadInterface(...)".

I'm not sure whether above make the code too complex, that's why I shutdown
DeviceSensorService-android here.

Please help to decide that should I add the "io_task_runner" in DeviceSensorHost
and DeviceSensorService? Thanks!

+  device::DeviceSensorService::GetInstance()->Shutdown();
+#endif
+}
 
 void DeviceService::OnStart() {}