Move JoinString to the base namespace

extensions/common/features/base_feature_provider.cc

Index: extensions/common/features/base_feature_provider.cc
diff --git a/extensions/common/features/base_feature_provider.cc b/extensions/common/features/base_feature_provider.cc
index 9d24d84ad085bc7d7badd9f3a3b1ce920c69e16c..472e1f55122b89a44fb7aa0973e7c6982560aa13 100644
--- a/extensions/common/features/base_feature_provider.cc
+++ b/extensions/common/features/base_feature_provider.cc
@@ -62,7 +62,7 @@ BaseFeatureProvider::BaseFeatureProvider(const base::DictionaryValue& root,
       std::stack<std::pair<std::string, const base::DictionaryValue*> >
           parse_stack;
       while (!split.empty()) {
-        std::string parent_name = JoinString(split, '.');
+        std::string parent_name = base::JoinString(split, ".");
         split.pop_back();
         if (root.HasKey(parent_name)) {
           const base::DictionaryValue* parent = nullptr;
@@ -176,7 +176,7 @@ Feature* BaseFeatureProvider::GetParent(Feature* feature) const {
   if (split.size() < 2)
     return nullptr;
   split.pop_back();
-  return GetFeature(JoinString(split, '.'));
+  return GetFeature(base::JoinString(split, "."));
 }
 
 // Children of a given API are named starting with parent.name()+".", which