Templatize ParseeGoogleMockStringFlag on String type.

src/gmock.cc

@@ -106,8 +106,9 @@ static bool ParseGoogleMockBoolFlag(const char* str, const char* flag,
 //
 // On success, stores the value of the flag in *value, and returns
 // true.  On failure, returns false without changing *value.
+template <typename String>
 static bool ParseGoogleMockStringFlag(const char* str, const char* flag,
-                                      std::string* value) {
+                                      String* value) {
   // Gets the value of the flag as a string.
   const char* const value_str = ParseGoogleMockFlagValue(str, flag, false);