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

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

BUG=367418
TEST=
R=rogerta@chromium.org,thakis@chromium.org

Review URL: https://codereview.chromium.org/1353323003

Cr-Commit-Position: refs/heads/master@{#349885}

rlz/chromeos/lib/rlz_value_store_chromeos.cc

@@ -61,15 +61,15 @@ base::FilePath GetRlzStoreLockPath() {
 }
 
 // Returns the dictionary key for storing access point-related prefs.
-std::string GetKeyName(std::string key, AccessPoint access_point) {
+std::string GetKeyName(const std::string& key, AccessPoint access_point) {
   std::string brand = SupplementaryBranding::GetBrand();
   if (brand.empty())
     brand = kNoSupplementaryBrand;
   return key + "." + GetAccessPointName(access_point) + "." + brand;
 }
 
 // Returns the dictionary key for storing product-related prefs.
-std::string GetKeyName(std::string key, Product product) {
+std::string GetKeyName(const std::string& key, Product product) {
   std::string brand = SupplementaryBranding::GetBrand();
   if (brand.empty())
     brand = kNoSupplementaryBrand;
@@ -242,7 +242,7 @@ void RlzValueStoreChromeOS::WriteStore() {
     LOG(ERROR) << "Error writing RLZ store";
 }
 
-bool RlzValueStoreChromeOS::AddValueToList(std::string list_name,
+bool RlzValueStoreChromeOS::AddValueToList(const std::string& list_name,
                                            base::Value* value) {
   base::ListValue* list_value = NULL;
   if (!rlz_store_->GetList(list_name, &list_value)) {
@@ -253,7 +253,7 @@ bool RlzValueStoreChromeOS::AddValueToList(std::string list_name,
   return true;
 }
 
-bool RlzValueStoreChromeOS::RemoveValueFromList(std::string list_name,
+bool RlzValueStoreChromeOS::RemoveValueFromList(const std::string& list_name,
                                                 const base::Value& value) {
   base::ListValue* list_value = NULL;
   if (!rlz_store_->GetList(list_name, &list_value))

rlz/chromeos/lib/rlz_value_store_chromeos.h

@@ -64,9 +64,10 @@ class RlzValueStoreChromeOS : public RlzValueStore,
   void WriteStore();
 
   // Adds |value| to list at |list_name| path in JSON store.
-  bool AddValueToList(std::string list_name, base::Value* value);
+  bool AddValueToList(const std::string& list_name, base::Value* value);
   // Removes |value| from list at |list_name| path in JSON store.
-  bool RemoveValueFromList(std::string list_name, const base::Value& value);
+  bool RemoveValueFromList(const std::string& list_name,
+                           const base::Value& value);
 
   // In-memory store with RLZ data.
   scoped_ptr<base::DictionaryValue> rlz_store_;