Replace device_sensor browsertest by service unittest.

services/device/device_service_test_base.cc

Index: services/device/device_service_test_base.cc
diff --git a/services/device/device_service_test_base.cc b/services/device/device_service_test_base.cc
index 595f669d9ce93f35533c3786dc811853ea1bacf0..2314b682d7328c22af77e3fa4a060e5f558e418a 100644
--- a/services/device/device_service_test_base.cc
+++ b/services/device/device_service_test_base.cc
@@ -5,9 +5,8 @@
 #include "services/device/device_service_test_base.h"
 
 #include <memory>
-
 #include "base/memory/ptr_util.h"
-#include "base/threading/thread.h"
+#include "base/memory/ref_counted.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "services/device/device_service.h"
 #include "services/device/public/interfaces/constants.mojom.h"
@@ -28,10 +27,12 @@ class ServiceTestClient : public service_manager::test::ServiceTestClient,
                           public service_manager::InterfaceFactory<
                               service_manager::mojom::ServiceFactory> {
  public:
-  explicit ServiceTestClient(service_manager::test::ServiceTest* test)
+  explicit ServiceTestClient(
+      service_manager::test::ServiceTest* test,
+      scoped_refptr<base::SingleThreadTaskRunner> io_task_runner)
       : service_manager::test::ServiceTestClient(test),
-        io_thread_("DeviceServiceTestIOThread"),
-        file_thread_("DeviceServiceTestFileThread") {
+        file_thread_("DeviceServiceTestFileThread"),
+        io_task_runner_(std::move(io_task_runner)) {
     registry_.AddInterface<service_manager::mojom::ServiceFactory>(this);
   }
   ~ServiceTestClient() override {}
@@ -47,18 +48,15 @@ class ServiceTestClient : public service_manager::test::ServiceTestClient,
   void CreateService(service_manager::mojom::ServiceRequest request,
                      const std::string& name) override {
     if (name == device::mojom::kServiceName) {
-      io_thread_.Start();
       file_thread_.Start();
 #if defined(OS_ANDROID)
       device_service_context_.reset(new service_manager::ServiceContext(
-          CreateDeviceService(file_thread_.task_runner(),
-                              io_thread_.task_runner(),
+          CreateDeviceService(file_thread_.task_runner(), io_task_runner_,
                               wake_lock_context_callback_),
           std::move(request)));
 #else
       device_service_context_.reset(new service_manager::ServiceContext(
-          CreateDeviceService(file_thread_.task_runner(),
-                              io_thread_.task_runner()),
+          CreateDeviceService(file_thread_.task_runner(), io_task_runner_),
           std::move(request)));
 #endif
     }
@@ -70,26 +68,38 @@ class ServiceTestClient : public service_manager::test::ServiceTestClient,
   }
 
  private:
-  base::Thread io_thread_;
   base::Thread file_thread_;
   service_manager::BinderRegistry registry_;
   mojo::BindingSet<service_manager::mojom::ServiceFactory>
       service_factory_bindings_;
   std::unique_ptr<service_manager::ServiceContext> device_service_context_;
 
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
   WakeLockContextCallback wake_lock_context_callback_;
 };
 
 }  // namespace
 
 DeviceServiceTestBase::DeviceServiceTestBase()
-    : ServiceTest(kTestServiceName) {}
+    : ServiceTest(kTestServiceName), io_thread_("DeviceServiceTestIOThread") {}
 
 DeviceServiceTestBase::~DeviceServiceTestBase() {}
 
 std::unique_ptr<service_manager::Service>
 DeviceServiceTestBase::CreateService() {
-  return base::MakeUnique<ServiceTestClient>(this);
+  // Instead of starting a new IO thread, we use the main thread to simulate
+  // the IO thread. This is because there are some sub-services in device
+  // (DeviceSensorService, for example) which are type of
+  // base::Singleton<base::LeakySingletonTraits>, this means the singleton
+  // instance is never deleted. When all the service unit test cases run in
+  // same process the singleton service instance stays alive across multiple
+  // unit test cases. There are some thread_checkers in the singleton
+  // instance so we have to make sure passing the same IO thread to
+  // each test case. We use the main thread to provide this consistency.
+
+  return base::MakeUnique<ServiceTestClient>(
+      this, base::ThreadTaskRunnerHandle::Get());
 }
 
 }  // namespace device