patchpanel: Remove the unused param in ShillClient::ScanDevices()

BUG=None
TEST=unit_tests

Change-Id: Ie03f3d5e72cfcbff68faa70fe5a583f182edd35f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2154293
Tested-by: Jie Jiang <jiejiang@chromium.org>
Commit-Queue: Jie Jiang <jiejiang@chromium.org>
Reviewed-by: Hugo Benichi <hugobenichi@google.com>
Reviewed-by: Garrick Evans <garrick@chromium.org>
diff --git a/patchpanel/arc_service.cc b/patchpanel/arc_service.cc
index 7bc40a6..7d86498 100644
--- a/patchpanel/arc_service.cc
+++ b/patchpanel/arc_service.cc
@@ -207,8 +207,7 @@
   AllocateAddressConfigs();
   shill_client_->RegisterDevicesChangedHandler(
       base::Bind(&ArcService::OnDevicesChanged, weak_factory_.GetWeakPtr()));
-  shill_client_->ScanDevices(
-      base::Bind(&ArcService::OnDevicesChanged, weak_factory_.GetWeakPtr()));
+  shill_client_->ScanDevices();
   shill_client_->RegisterDefaultInterfaceChangedHandler(base::Bind(
       &ArcService::OnDefaultInterfaceChanged, weak_factory_.GetWeakPtr()));
 }
diff --git a/patchpanel/shill_client.cc b/patchpanel/shill_client.cc
index 18b0ca5..5f7a145 100644
--- a/patchpanel/shill_client.cc
+++ b/patchpanel/shill_client.cc
@@ -34,7 +34,7 @@
   return devices_.find(ifname) != devices_.end();
 }
 
-void ShillClient::ScanDevices(const DevicesChangeHandler& handler) {
+void ShillClient::ScanDevices() {
   brillo::VariantDictionary props;
   if (!manager_proxy_->GetProperties(&props, nullptr)) {
     LOG(ERROR) << "Unable to get manager properties";
diff --git a/patchpanel/shill_client.h b/patchpanel/shill_client.h
index 342edd9..cf4f79dc 100644
--- a/patchpanel/shill_client.h
+++ b/patchpanel/shill_client.h
@@ -34,7 +34,7 @@
 
   void RegisterDevicesChangedHandler(const DevicesChangeHandler& handler);
 
-  void ScanDevices(const DevicesChangeHandler& handler);
+  void ScanDevices();
 
   // Returns the cached interface name; does not initiate a property fetch.
   virtual const std::string& default_interface() const;