Replace OStream with std::ostream.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 3ed6623e9d6617e88aa2cfff3df53388c380f28c..c9a23fd22868f928df88ac0474cadae1bdb6341d 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.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_IA32
@@ -365,9 +367,9 @@ LOperand* LPlatformChunk::GetNextSpillSlot(RegisterKind kind) {
 
 void LStoreNamedField::PrintDataTo(StringStream* stream) {
   object()->PrintTo(stream);
-  OStringStream os;
+  std::ostringstream os;
   os << hydrogen()->access() << " <- ";
-  stream->Add(os.c_str());
+  stream->Add(os.str().c_str());
   value()->PrintTo(stream);
 }