Replace OStream with std::ostream.

src/flags.cc

Index: src/flags.cc
diff --git a/src/flags.cc b/src/flags.cc
index 98f21ef2c4c9e9ba4c7cf1adcec58593ef234709..e53c45e69d3a35e904f6853035cf6f7c24826f12 100644
--- a/src/flags.cc
+++ b/src/flags.cc
@@ -2,8 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <ctype.h>
-#include <stdlib.h>
+#include <cctype>
+#include <cstdlib>
+#include <sstream>
 
 #include "src/v8.h"
 
@@ -181,7 +182,7 @@ static const char* Type2String(Flag::FlagType type) {
 }
 
 
-OStream& operator<<(OStream& os, const Flag& flag) {  // NOLINT
+std::ostream& operator<<(std::ostream& os, const Flag& flag) {  // NOLINT
   switch (flag.type()) {
     case Flag::TYPE_BOOL:
       os << (*flag.bool_variable() ? "true" : "false");
@@ -231,21 +232,21 @@ List<const char*>* FlagList::argv() {
       }
       {
         bool disabled = f->type() == Flag::TYPE_BOOL && !*f->bool_variable();
-        OStringStream os;
+        std::ostringstream os;
         os << (disabled ? "--no" : "--") << f->name();
-        args->Add(StrDup(os.c_str()));
+        args->Add(StrDup(os.str().c_str()));
       }
       if (f->type() != Flag::TYPE_BOOL) {
-        OStringStream os;
+        std::ostringstream os;
         os << *f;
-        args->Add(StrDup(os.c_str()));
+        args->Add(StrDup(os.str().c_str()));
       }
     }
   }
   if (args_flag != NULL) {
-    OStringStream os;
+    std::ostringstream os;
     os << "--" << args_flag->name();
-    args->Add(StrDup(os.c_str()));
+    args->Add(StrDup(os.str().c_str()));
     JSArguments jsargs = *args_flag->args_variable();
     for (int j = 0; j < jsargs.argc; j++) {
       args->Add(StrDup(jsargs[j]));