Replace wstring with string16 in sandbox

sandbox/win/tests/common/controller.h

Index: sandbox/win/tests/common/controller.h
diff --git a/sandbox/win/tests/common/controller.h b/sandbox/win/tests/common/controller.h
index 6c143e561e1f02ccd6d96a925b16b6ae9345e339..03bfa307d232c129056fbbae09a400fb3da21e85 100644
--- a/sandbox/win/tests/common/controller.h
+++ b/sandbox/win/tests/common/controller.h
@@ -8,6 +8,7 @@
 #include <windows.h>
 #include <string>
 
+#include "base/strings/string16.h"
 #include "base/win/scoped_handle.h"
 #include "sandbox/win/src/sandbox.h"
 
@@ -148,7 +149,7 @@ class TestRunner {
 BrokerServices* GetBroker();
 
 // Constructs a full path to a file inside the system32 (or syswow64) folder.
-std::wstring MakePathToSys(const wchar_t* name, bool is_obj_man_path);
+base::string16 MakePathToSys(const wchar_t* name, bool is_obj_man_path);
 
 // Runs the given test on the target process.
 int DispatchCall(int argc, wchar_t **argv);