Enable positional parameters for base::vsnprintf and base::vswprintf on Windows.

base/stringprintf_unittest.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/basictypes.h"
 #include "base/stringprintf.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
@@ skipping 131 matching lines @@
   wchar_t invalid[2];
   invalid[0] = 0xffff;
   invalid[1] = 0;
 
   std::wstring out;
   SStringPrintf(&out, L"%ls", invalid);
   EXPECT_STREQ(L"", out.c_str());
 }
 #endif
 
+// Test that the positional parameters work.
+TEST(StringPrintfTest, PositionalParameters) {
+  std::string out;
+  SStringPrintf(&out, "%1$s %1$s", "test");
+  EXPECT_STREQ("test test", out.c_str());
+
+#if defined(OS_WIN)
+  std::wstring wout;
+  SStringPrintf(&wout, L"%1$ls %1$ls", L"test");
+  EXPECT_STREQ(L"test test", wout.c_str());
+#endif
+}
+
 }  // namespace base