Fix the build.

llvm-svn: 43057
diff --git a/clang/Driver/SerializationTest.cpp b/clang/Driver/SerializationTest.cpp
index 35ef4b7..a18bd22 100644
--- a/clang/Driver/SerializationTest.cpp
+++ b/clang/Driver/SerializationTest.cpp
@@ -21,6 +21,7 @@
 #include "llvm/System/Path.h"
 #include "llvm/Bitcode/BitstreamWriter.h"
 #include <fstream>
+#include <iostream>
 
 using namespace clang;
 using llvm::BitstreamWriter;