Add missing include to test_support.h.

mojo/public/cpp/test_support/test_support.h

 // Copyright 2014 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.
 
 // Support functions for running "internal" tests. These functions are not for
 // public consumption.
 
 #ifndef MOJO_PUBLIC_CPP_TEST_SUPPORT_TEST_SUPPORT_H_
 #define MOJO_PUBLIC_CPP_TEST_SUPPORT_TEST_SUPPORT_H_
 
+#include <stdio.h>
+
 #include <string>
 #include <vector>
 
 namespace mojo {
 namespace test {
 
 // Logs the result of a perf test. (|sub_test_name| is optional and may be
 // null.) You may only call this while running inside a perf test suite.
 void LogPerfResult(const char* test_name,
                    const char* sub_test_name,
                    double value,
                    const char* units);
 
 // Opens a text file given by a path relative to the source root for reading.
 FILE* OpenSourceRootRelativeFile(const std::string& relative_path);
 
 // Returns the list of regular files in a directory given by a path relative to
 // the source root. (The result only includes the filenames, not the path.)
 std::vector<std::string> EnumerateSourceRootRelativeDirectory(
     const std::string& relative_path);
 
 }  // namespace test
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_TEST_SUPPORT_TEST_SUPPORT_H_