Refactor audio and video decoder status into common file.

media/base/decode_status.h

+// 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_BASE_DECODE_STATUS_H_
+#define MEDIA_BASE_DECODE_STATUS_H_
+
+#include <iosfwd>
+
+#include "media/base/media_export.h"
+
+namespace media {
+
+enum class DecodeStatus {
+  OK = 0,        // Everything went as planned.
+  ABORTED,       // Read aborted due to Reset() during pending read.
+  DECODE_ERROR,  // Decoder returned decode error. Note: Prefixed by DECODE_
+                 // since ERROR is a reserved name (special macro) on Windows.
+};
+
+// Helper function so that DecodeStatus can be printed easily.
+MEDIA_EXPORT std::ostream& operator<<(std::ostream& os,
+                                      const DecodeStatus& status);
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_DECODE_STATUS_H_