Cleanup: Pass std::string as const reference from chromeos/

Passing std::string by reference can prevent extra copying of object.

BUG=367418
TEST=
R=zelidrag@chromium.org,derat@chromium.org,gauravsh@chromium.org

Review URL: https://codereview.chromium.org/1353323002

Cr-Commit-Position: refs/heads/master@{#350078}

9 files changed, 20 insertions, 13 deletions

diff --git a/chromeos/audio/audio_devices_pref_handler_impl.cc b/chromeos/audio/audio_devices_pref_handler_impl.cc
index 4e72de6..17b5681 100644
--- a/chromeos/audio/audio_devices_pref_handler_impl.cc
+++ b/chromeos/audio/audio_devices_pref_handler_impl.cc
@@ -187,14 +187,14 @@ void AudioDevicesPrefHandlerImpl::SaveDevicesVolumePref() {
 }
 
 void AudioDevicesPrefHandlerImpl::MigrateDeviceMuteSettings(
-    std::string active_device) {
+    const std::string& active_device) {
   int old_mute = local_state_->GetInteger(prefs::kAudioMute);
   device_mute_settings_->SetInteger(active_device, old_mute);
   SaveDevicesMutePref();
 }
 
 void AudioDevicesPrefHandlerImpl::MigrateDeviceVolumeSettings(
-    std::string active_device) {
+    const std::string& active_device) {
   double old_volume = local_state_->GetDouble(prefs::kAudioVolumePercent);
   device_volume_settings_->SetDouble(active_device, old_volume);
   SaveDevicesVolumePref();
diff --git a/chromeos/audio/audio_devices_pref_handler_impl.h b/chromeos/audio/audio_devices_pref_handler_impl.h
index aeb9f3e..72dc335 100644
--- a/chromeos/audio/audio_devices_pref_handler_impl.h
+++ b/chromeos/audio/audio_devices_pref_handler_impl.h
@@ -64,8 +64,8 @@ class CHROMEOS_EXPORT AudioDevicesPrefHandlerImpl
   // previous global pref value to the new per device pref value for the
   // current active device. If a previous global setting doesn't exist, we'll
   // use default values of mute = off and volume = 75%.
-  void MigrateDeviceMuteSettings(std::string active_device);
-  void MigrateDeviceVolumeSettings(std::string active_device);
+  void MigrateDeviceMuteSettings(const std::string& active_device);
+  void MigrateDeviceVolumeSettings(const std::string& active_device);
 
   // Notifies the AudioPrefObserver for audio policy pref changes.
   void NotifyAudioPolicyChange();
diff --git a/chromeos/dbus/fake_shill_manager_client.cc b/chromeos/dbus/fake_shill_manager_client.cc
index 337041b..ca7c6a5 100644
--- a/chromeos/dbus/fake_shill_manager_client.cc
+++ b/chromeos/dbus/fake_shill_manager_client.cc
@@ -1115,8 +1115,9 @@ bool FakeShillManagerClient::ParseOption(const std::string& arg0,
   return SetInitialNetworkState(arg0, arg1);
 }
 
-bool FakeShillManagerClient::SetInitialNetworkState(std::string type_arg,
-                                                    std::string state_arg) {
+bool FakeShillManagerClient::SetInitialNetworkState(
+    std::string type_arg,
+    const std::string& state_arg) {
   int state_arg_as_int = -1;
   base::StringToInt(state_arg, &state_arg_as_int);
 
diff --git a/chromeos/dbus/fake_shill_manager_client.h b/chromeos/dbus/fake_shill_manager_client.h
index 313a2d4..f677350 100644
--- a/chromeos/dbus/fake_shill_manager_client.h
+++ b/chromeos/dbus/fake_shill_manager_client.h
@@ -126,7 +126,8 @@ class CHROMEOS_EXPORT FakeShillManagerClient
   // {wifi,cellular,etc}={on,off,disabled,none} - sets initial state for type
   void ParseCommandLineSwitch();
   bool ParseOption(const std::string& arg0, const std::string& arg1);
-  bool SetInitialNetworkState(std::string type_arg, std::string state_arg);
+  bool SetInitialNetworkState(std::string type_arg,
+                              const std::string& state_arg);
   std::string GetInitialStateForType(const std::string& type,
                                      bool* enabled);
 
diff --git a/chromeos/network/network_connection_handler.h b/chromeos/network/network_connection_handler.h
index ddadf7a..8b4e93f 100644
--- a/chromeos/network/network_connection_handler.h
+++ b/chromeos/network/network_connection_handler.h
@@ -193,7 +193,11 @@ class CHROMEOS_EXPORT NetworkConnectionHandler
                                  const std::string& error_name,
                                  const std::string& error_message);
 
+  // Note: |service_path| is passed by value here, because in some cases
+  // the value may be located in the map and then it can be deleted, producing
+  // a reference to invalid memory.
   void CheckPendingRequest(const std::string service_path);
+
   void CheckAllPendingRequests();
 
   // Notify caller and observers that the connect request succeeded.
diff --git a/chromeos/network/onc/onc_certificate_importer_impl_unittest.cc b/chromeos/network/onc/onc_certificate_importer_impl_unittest.cc
index 35ff424..caa5ed8 100644
--- a/chromeos/network/onc/onc_certificate_importer_impl_unittest.cc
+++ b/chromeos/network/onc/onc_certificate_importer_impl_unittest.cc
@@ -97,7 +97,8 @@ class ONCCertificateImporterImplTest : public testing::Test {
     web_trust_certificates_ = onc_trusted_certificates;
   }
 
-  void AddCertificatesFromFile(std::string filename, bool expected_success) {
+  void AddCertificatesFromFile(const std::string& filename,
+                               bool expected_success) {
     scoped_ptr<base::DictionaryValue> onc =
         test_utils::ReadTestDictionary(filename);
     scoped_ptr<base::Value> certificates_value;
@@ -122,7 +123,7 @@ class ONCCertificateImporterImplTest : public testing::Test {
     private_list_ = ListCertsInPrivateSlot();
   }
 
-  void AddCertificateFromFile(std::string filename,
+  void AddCertificateFromFile(const std::string& filename,
                               net::CertType expected_type,
                               std::string* guid) {
     std::string guid_temporary;
diff --git a/chromeos/network/shill_property_util.cc b/chromeos/network/shill_property_util.cc
index 30a6925..c5cafc8 100644
--- a/chromeos/network/shill_property_util.cc
+++ b/chromeos/network/shill_property_util.cc
@@ -61,7 +61,7 @@ bool CopyStringFromDictionary(const base::DictionaryValue& source,
 
 }  // namespace
 
-void SetSSID(const std::string ssid, base::DictionaryValue* properties) {
+void SetSSID(const std::string& ssid, base::DictionaryValue* properties) {
   std::string hex_ssid = base::HexEncode(ssid.c_str(), ssid.size());
   properties->SetStringWithoutPathExpansion(shill::kWifiHexSsid, hex_ssid);
 }
diff --git a/chromeos/network/shill_property_util.h b/chromeos/network/shill_property_util.h
index cc9da9c..f585da4 100644
--- a/chromeos/network/shill_property_util.h
+++ b/chromeos/network/shill_property_util.h
@@ -22,7 +22,7 @@ class NetworkUIData;
 namespace shill_property_util {
 
 // Sets the |ssid| in |properties|.
-CHROMEOS_EXPORT void SetSSID(const std::string ssid,
+CHROMEOS_EXPORT void SetSSID(const std::string& ssid,
                              base::DictionaryValue* properties);
 
 // Returns the SSID from |properties| in UTF-8 encoding. If |verbose_logging| is
diff --git a/chromeos/tools/onc_validator/onc_validator.cc b/chromeos/tools/onc_validator/onc_validator.cc
index 84a9220..14ed891 100644
--- a/chromeos/tools/onc_validator/onc_validator.cc
+++ b/chromeos/tools/onc_validator/onc_validator.cc
@@ -82,7 +82,7 @@ void PrintHelp() {
           kStatusArgumentError);
 }
 
-scoped_ptr<base::DictionaryValue> ReadDictionary(std::string filename) {
+scoped_ptr<base::DictionaryValue> ReadDictionary(const std::string& filename) {
   base::FilePath path(filename);
   JSONFileValueDeserializer deserializer(path);
   deserializer.set_allow_trailing_comma(true);
@@ -151,7 +151,7 @@ int main(int argc, const char* argv[]) {
   chromeos::onc::Validator::Result result;
   validator.ValidateAndRepairObject(signature, *onc_object, &result);
 
-  switch(result) {
+  switch (result) {
     case chromeos::onc::Validator::VALID:
       return kStatusValid;
     case chromeos::onc::Validator::VALID_WITH_WARNINGS: