Fix clang-tidy warnings in apmanager.
am: 2946762690

Change-Id: I4eaba8276e2f6fb0e1a0a935c869ce0de63cf304
diff --git a/device_info.cc b/device_info.cc
index 706a161..afdd8c2 100644
--- a/device_info.cc
+++ b/device_info.cc
@@ -317,7 +317,7 @@
   device->RegisterInterface(iter->second);
 }
 
-void DeviceInfo::RegisterDevice(scoped_refptr<Device> device) {
+void DeviceInfo::RegisterDevice(const scoped_refptr<Device>& device) {
   if (!device) {
     return;
   }
diff --git a/device_info.h b/device_info.h
index 937359f..83faa2a 100644
--- a/device_info.h
+++ b/device_info.h
@@ -93,7 +93,7 @@
       uint32_t iface_index, const shill::Nl80211Message& msg);
 
   scoped_refptr<Device> GetDevice(const std::string& phy_name);
-  void RegisterDevice(scoped_refptr<Device> device);
+  void RegisterDevice(const scoped_refptr<Device>& device);
 
   // Maps interface index to interface info
   std::map<uint32_t, Device::WiFiInterface> interface_infos_;
diff --git a/device_info_unittest.cc b/device_info_unittest.cc
index 157d1be..4f98661 100644
--- a/device_info_unittest.cc
+++ b/device_info_unittest.cc
@@ -148,7 +148,7 @@
     device_info_.OnWiFiInterfacePhyInfoReceived(interface_index, message);
   }
 
-  void RegisterDevice(scoped_refptr<Device> device) {
+  void RegisterDevice(const scoped_refptr<Device>& device) {
     device_info_.RegisterDevice(device);
   }
 
diff --git a/device_unittest.cc b/device_unittest.cc
index 585e9f2..72f2c98 100644
--- a/device_unittest.cc
+++ b/device_unittest.cc
@@ -78,7 +78,7 @@
     EXPECT_EQ(interface_name, device_->GetPreferredApInterface());
   }
 
-  void AddWiphyBandAttribute(shill::AttributeListRefPtr wiphy_bands,
+  void AddWiphyBandAttribute(const shill::AttributeListRefPtr& wiphy_bands,
                              const std::string& band_name,
                              int band_id,
                              std::vector<uint32_t> frequency_list,
diff --git a/error_unittest.cc b/error_unittest.cc
index 7e51c08..2550f04 100644
--- a/error_unittest.cc
+++ b/error_unittest.cc
@@ -41,7 +41,7 @@
     error->type_ = type;
   }
 
-  void PopulateError(Error* error, Error::Type type, string message) {
+  void PopulateError(Error* error, Error::Type type, const string& message) {
     error->type_ = type;
     error->message_ = message;
   }
diff --git a/manager_unittest.cc b/manager_unittest.cc
index 91bbc20..f959d98 100644
--- a/manager_unittest.cc
+++ b/manager_unittest.cc
@@ -35,7 +35,7 @@
         .WillByDefault(ReturnNew<FakeDeviceAdaptor>());
   }
 
-  void RegisterDevice(scoped_refptr<Device> device) {
+  void RegisterDevice(const scoped_refptr<Device>& device) {
     manager_.devices_.push_back(device);
   }
 
diff --git a/mock_config.h b/mock_config.h
index ec657b5..25348e7 100644
--- a/mock_config.h
+++ b/mock_config.h
@@ -28,7 +28,7 @@
 
 class MockConfig : public Config {
  public:
-  MockConfig(Manager* manager);
+  explicit MockConfig(Manager* manager);
   ~MockConfig() override;
 
   MOCK_METHOD2(GenerateConfigFile,