Convert utility process ParseMediaMetadata IPC to mojo

chrome/common/extensions/media_parser.mojom

+// 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.
+
+// Media parsing interface provided by the utility process and exposed by
+// mojo policy control to the chrome browser process.
+
+module extensions.mojom;
+
+import "mojo/common/values.mojom";
+
+struct AttachedImage {
+  string type;

[tibell, 2017/01/09 03:55:51]

Is this a MIME type? Please add a comment and perhaps rename to mime_type for
clarity.

[Noel Gordon, 2017/01/09 14:54:19]

Not sure it's a mime type: no documentation in ::media::AttachedImage about it.

+  string data;

[tibell, 2017/01/09 03:55:51]

If this is binary data use array<uint8>. string will be string in C++, but a
Unicode thing in Java.

[Noel Gordon, 2017/01/09 14:54:19]

Looks like binary data, so good point; use an array<uint8>.

I used a ConstCArray<uint8_t> to put the std::string on to the wire as an
array<uint8>, and a mojo data view of the structure's .data field to read it off
the wire back into a std::string.

Re-tested, seems fine. Though the code now has reintepret_cast() in a few
places, array<uint8> is a much better type to use here, well-spotted.

+};
+
+interface MediaParser {
+  ParseMediaMetadata(string mime_type,
+                     int64 total_size,
+                     bool get_attached_images)
+      => (bool parse_success,
+          mojo.common.mojom.DictionaryValue metadata,
+          array<AttachedImage> attached_images);
+};