Cleanup: Remove wstring methods from base::Pickle.

ipc/ipc_message_utils.h

Index: ipc/ipc_message_utils.h
diff --git a/ipc/ipc_message_utils.h b/ipc/ipc_message_utils.h
index d4c6268ba0f6fdff252f500c38130fe9cf8c076a..597729705a952ca4c6ef5c3c6262c92036b77b52 100644
--- a/ipc/ipc_message_utils.h
+++ b/ipc/ipc_message_utils.h
@@ -251,22 +251,6 @@ struct ParamTraits<std::string> {
 };
 
 template <>
-struct ParamTraits<std::wstring> {
-  typedef std::wstring param_type;
-  static void Write(Message* m, const param_type& p) {
-    m->WriteWString(p);
-  }
-  static bool Read(const Message* m, PickleIterator* iter,
-                   param_type* r) {
-    return iter->ReadWString(r);
-  }
-  IPC_EXPORT static void Log(const param_type& p, std::string* l);
-};
-
-// If WCHAR_T_IS_UTF16 is defined, then string16 is a std::wstring so we don't
-// need this trait.
-#if !defined(WCHAR_T_IS_UTF16)
-template <>
 struct ParamTraits<base::string16> {
   typedef base::string16 param_type;
   static void Write(Message* m, const param_type& p) {
@@ -278,7 +262,6 @@ struct ParamTraits<base::string16> {
   }
   IPC_EXPORT static void Log(const param_type& p, std::string* l);
 };
-#endif
 
 template <>
 struct IPC_EXPORT ParamTraits<std::vector<char> > {