Remove usage of FOR_EACH_OBSERVER macro in device/

device/usb/usb_service.cc

Index: device/usb/usb_service.cc
diff --git a/device/usb/usb_service.cc b/device/usb/usb_service.cc
index b6e6dca0667c93fef1912fd241d46eae47a62967..1a2cf98c303515444602a615cffe05c55839ce07 100644
--- a/device/usb/usb_service.cc
+++ b/device/usb/usb_service.cc
@@ -53,7 +53,8 @@ std::unique_ptr<UsbService> UsbService::Create(
 UsbService::~UsbService() {
   for (const auto& map_entry : devices_)
     map_entry.second->OnDisconnect();
-  FOR_EACH_OBSERVER(Observer, observer_list_, WillDestroyUsbService());
+  for (auto& observer : observer_list_)
+    observer.WillDestroyUsbService();
 }
 
 UsbService::UsbService(
@@ -127,15 +128,18 @@ void UsbService::GetTestDevices(
 void UsbService::NotifyDeviceAdded(scoped_refptr<UsbDevice> device) {
   DCHECK(CalledOnValidThread());
 
-  FOR_EACH_OBSERVER(Observer, observer_list_, OnDeviceAdded(device));
+  for (auto& observer : observer_list_)
+    observer.OnDeviceAdded(device);
 }
 
 void UsbService::NotifyDeviceRemoved(scoped_refptr<UsbDevice> device) {
   DCHECK(CalledOnValidThread());
 
-  FOR_EACH_OBSERVER(Observer, observer_list_, OnDeviceRemoved(device));
+  for (auto& observer : observer_list_)
+    observer.OnDeviceRemoved(device);
   device->NotifyDeviceRemoved();
-  FOR_EACH_OBSERVER(Observer, observer_list_, OnDeviceRemovedCleanup(device));
+  for (auto& observer : observer_list_)
+    observer.OnDeviceRemovedCleanup(device);
 }
 
 }  // namespace device