EDK: Add mojo::util::StringPrintf() (etc.) and convert away from base's.

mojo/edk/util/string_printf.h

Index: mojo/edk/util/string_printf.h
diff --git a/mojo/edk/util/string_printf.h b/mojo/edk/util/string_printf.h
new file mode 100644
index 0000000000000000000000000000000000000000..584b5b9aa3fa923ee5196ddc0d143a655ff4b324
--- /dev/null
+++ b/mojo/edk/util/string_printf.h
@@ -0,0 +1,38 @@
+// Copyright 2013 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.
+
+// |printf()|-like formatting functions that output/append to C++ strings.
+//
+// TODO(vtl): We don't have the |PRINTF_FORMAT()| macros/warnings like
+// Chromium's version -- should we? (I've rarely seen them being useful.)
+
+#ifndef MOJO_EDK_UTIL_STRING_PRINTF_H_
+#define MOJO_EDK_UTIL_STRING_PRINTF_H_
+
+#include <stdarg.h>
+
+#include <string>
+
+#include "mojo/public/c/system/macros.h"
+
+namespace mojo {
+namespace util {
+
+// Formats |printf()|-like input and returns it as an |std::string|.
+std::string StringPrintf(const char* format, ...) MOJO_WARN_UNUSED_RESULT;
+
+// Formats |vprintf()|-like input and returns it as an |std::string|.
+std::string StringVPrintf(const char* format,
+                          va_list ap) MOJO_WARN_UNUSED_RESULT;
+
+// Formats |printf()|-like input and appends it to |*dest|.
+void StringAppendf(std::string* dest, const char* format, ...);
+
+// Formats |vprintf()|-like input and appends it to |*dest|.
+void StringVAppendf(std::string* dest, const char* format, va_list ap);
+
+}  // namespace util
+}  // namespace mojo
+
+#endif  // MOJO_EDK_UTIL_STRING_PRINTF_H_