media: Plumb MediaLog to MojoVideoDecoderService.

media/mojo/interfaces/media_log.mojom

Index: media/mojo/interfaces/media_log.mojom
diff --git a/media/mojo/interfaces/media_log.mojom b/media/mojo/interfaces/media_log.mojom
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index 0000000000000000000000000000000000000000..05f3b64c9806177c6c392faae17dd700ef68249c
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+// Copyright 2017 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.
+
+module media.mojom;
+
+import "media/mojo/interfaces/media_types.mojom";
+
+interface MediaLog {
+  AddEvent(MediaLogEvent event);
+};