Replace OStream with std::ostream.

src/compiler/x64/instruction-selector-x64-unittest.cc

Index: src/compiler/x64/instruction-selector-x64-unittest.cc
diff --git a/src/compiler/x64/instruction-selector-x64-unittest.cc b/src/compiler/x64/instruction-selector-x64-unittest.cc
index cc2fedb3fcf3707acc20f54f02fac34145a69864..fce4da9225b51ff6b1772b53ed0a77ac057d53a3 100644
--- a/src/compiler/x64/instruction-selector-x64-unittest.cc
+++ b/src/compiler/x64/instruction-selector-x64-unittest.cc
@@ -108,9 +108,7 @@ struct MemoryAccess {
 
 
 std::ostream& operator<<(std::ostream& os, const MemoryAccess& memacc) {
-  OStringStream ost;
-  ost << memacc.type;
-  return os << ost.c_str();
+  return os << memacc.type;
 }
 
 
@@ -303,9 +301,7 @@ struct MultParam {
 
 
 std::ostream& operator<<(std::ostream& os, const MultParam& m) {
-  OStringStream ost;
-  ost << m.value << "." << m.lea_expected << "." << m.addressing_mode;
-  return os << ost.c_str();
+  return os << m.value << "." << m.lea_expected << "." << m.addressing_mode;
 }