string_util support for joining strings using strings not just chars.

base/string_util.cc

Index: base/string_util.cc
diff --git a/base/string_util.cc b/base/string_util.cc
index 2eecb79eaa77ea027ff436b496e77b0b90a4a023..9e3422d260237902d562c03174fc755850387683 100644
--- a/base/string_util.cc
+++ b/base/string_util.cc
@@ -750,8 +750,7 @@ size_t Tokenize(const base::StringPiece& str,
 }
 
 template<typename STR>
-static STR JoinStringT(const std::vector<STR>& parts,
-                       typename STR::value_type sep) {
+static STR JoinStringT(const std::vector<STR>& parts, const STR& sep) {
   if (parts.empty())
     return STR();
 
@@ -768,11 +767,21 @@ static STR JoinStringT(const std::vector<STR>& parts,
 }
 
 std::string JoinString(const std::vector<std::string>& parts, char sep) {
-  return JoinStringT(parts, sep);
+  return JoinStringT(parts, std::string(1, sep));
 }
 
 string16 JoinString(const std::vector<string16>& parts, char16 sep) {
-  return JoinStringT(parts, sep);
+  return JoinStringT(parts, string16(1, sep));
+}
+
+std::string JoinString(const std::vector<std::string>& parts,
+                       const std::string& separator) {
+  return JoinStringT(parts, separator);
+}
+
+string16 JoinString(const std::vector<string16>& parts,
+                    const string16& separator) {
+  return JoinStringT(parts, separator);
 }
 
 template<class FormatStringType, class OutStringType>