MIPS: Replace OStream with std::ostream.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 3f95d4ba6db2c65382790181793ce32889edf333..7002ca4c08a57788645de759a85e8909ba10c654 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <sstream>
+
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_MIPS
@@ -325,7 +327,7 @@ void LStoreNamedField::PrintDataTo(StringStream* stream) {
   object()->PrintTo(stream);
   std::ostringstream os;
   os << hydrogen()->access() << " <- ";
-  stream->Add(os.c_str());
+  stream->Add(os.str().c_str());
   value()->PrintTo(stream);
 }