Add media file validation to utility process

media/base/media_file_checker.h

+// 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.
+
+#ifndef MEDIA_BASE_MEDIA_FILE_CHECKER_H_
+#define MEDIA_BASE_MEDIA_FILE_CHECKER_H_
+
+#include "base/basictypes.h"
+#include "base/files/scoped_platform_file_closer.h"
+#include "base/platform_file.h"
+#include "media/base/media_export.h"
+
+namespace base {
+class TimeDelta;
+}
+
+namespace media {
+
+// Open and read |file| to determine if it appears to be a valid media file.

[DaleCurtis, 2013/08/08 21:04:33]

Sounds like this comment should go with the constructor and a higher level
comment should be here.

[vandebo (ex-Chrome), 2013/08/08 23:04:18]

Rephrased comment.

+// The entire file is not decoded so a positive result from this class does
+// not make the file safe to use in the browser process.
+class MEDIA_EXPORT MediaFileChecker {
+ public:
+  explicit MediaFileChecker(base::PlatformFile file);

[DaleCurtis, 2013/08/08 21:04:33]

Should this be const&?

[vandebo (ex-Chrome), 2013/08/08 23:04:18]

Done.

+  ~MediaFileChecker();
+
+  // After opening |file|, up to |check_time| amount of wall-clock time is spent
+  // decoding the file. The amount of audio/video data decoded will depend on
+  // the bitrate of the file and the speed of the CPU.
+  bool Start(const base::TimeDelta& check_time);

[DaleCurtis, 2013/08/08 21:04:33]

Time structs are just int64s in the end, so it's not necessary to const& -- see
usage pattern in time.h for reference.

[vandebo (ex-Chrome), 2013/08/08 23:04:18]

Done.

+
+ private:
+  base::PlatformFile file_;
+  base::ScopedPlatformFileCloser file_closer_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaFileChecker);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_MEDIA_FILE_CHECKER_H_