Replace wstring with string16 in sandbox

sandbox/win/src/sandbox_policy.h

Index: sandbox/win/src/sandbox_policy.h
diff --git a/sandbox/win/src/sandbox_policy.h b/sandbox/win/src/sandbox_policy.h
index 733356a39b89787bc3caf5e02c80d993871caf6b..a9f124516218ae00cebb1f42cf58bd7250798234 100644
--- a/sandbox/win/src/sandbox_policy.h
+++ b/sandbox/win/src/sandbox_policy.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/strings/string16.h"
 #include "sandbox/win/src/sandbox_types.h"
 #include "sandbox/win/src/security_level.h"
 
@@ -129,7 +130,7 @@ class TargetPolicy {
   // Returns the name of the alternate desktop used. If an alternate window
   // station is specified, the name is prepended by the window station name,
   // followed by a backslash.
-  virtual std::wstring GetAlternateDesktop() const = 0;
+  virtual base::string16 GetAlternateDesktop() const = 0;
 
   // Precreates the desktop and window station, if any.
   virtual ResultCode CreateAlternateDesktop(bool alternate_winstation) = 0;