[sensors] Introduce asynchronous way to create sensors.

device/generic_sensor/fake_platform_sensor_provider.cc

Index: device/generic_sensor/fake_platform_sensor_provider.cc
diff --git a/device/generic_sensor/fake_platform_sensor_provider.cc b/device/generic_sensor/fake_platform_sensor_provider.cc
index 920ea5d9472e898f5f9fcf485a61cd0353d9578b..37c19de5bbe05443ec07315a10bd3362b35638a1 100644
--- a/device/generic_sensor/fake_platform_sensor_provider.cc
+++ b/device/generic_sensor/fake_platform_sensor_provider.cc
@@ -20,11 +20,14 @@ FakePlatformSensorProvider::FakePlatformSensorProvider() = default;
 
 FakePlatformSensorProvider::~FakePlatformSensorProvider() = default;
 
-scoped_refptr<PlatformSensor> FakePlatformSensorProvider::CreateSensorInternal(
+void FakePlatformSensorProvider::CreateSensorInternal(
     mojom::SensorType type,
     mojo::ScopedSharedBufferMapping mapping,
-    uint64_t buffer_size) {
-  return new FakePlatformSensor(type, std::move(mapping), buffer_size, this);
+    uint64_t buffer_size,
+    const CreateSensorCallback& callback) {
+  scoped_refptr<FakePlatformSensor> sensor =
+      new FakePlatformSensor(type, std::move(mapping), buffer_size, this);
+  callback.Run(std::move(sensor));
 }
 
 }  // namespace device