Use passthrough decoder for (E)AC3 formats

media/formats/ac3/ac3_util.h

Index: media/formats/ac3/ac3_util.h
diff --git a/media/formats/ac3/ac3_util.h b/media/formats/ac3/ac3_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..3cd9dcd5e681e8a3dc7e9f5ea72841a8660799d9
--- /dev/null
+++ b/media/formats/ac3/ac3_util.h
@@ -0,0 +1,31 @@
+// Copyright 2016 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_FORMATS_AC3_AC3_UTIL_H_
+#define MEDIA_FORMATS_AC3_AC3_UTIL_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "base/macros.h"
+
+namespace media {
+
+class Ac3Util {
+ public:
+  // Returns the total number of audio samples in the given buffer, which
+  // contains several complete AC3 syncframes.
+  static int ParseTotalAc3SampleCount(const uint8_t* data, size_t size);
+
+  // Returns the total number of audio samples in the given buffer, which
+  // contains several complete E-AC3 syncframes.
+  static int ParseTotalEac3SampleCount(const uint8_t* data, size_t size);
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Ac3Util);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FORMATS_AC3_AC3_UTIL_H_