Convert utility process ParseMediaMetadata blob reading 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/file.mojom";
 import "mojo/common/time.mojom";
 import "mojo/common/values.mojom";
 
-struct AttachedImage {
-  string type;
-  array<uint8> data;
-};
-
 interface MediaParser {
+  // Extract metadata from a |mime_type| blob of data of |total_size| and
+  // available from the browser process via |media_data_source|. If there
+  // are images referred to in the metadata, and |get_attached_images| is
+  // true, return the images in |attached_images|.
   ParseMediaMetadata(string mime_type,
                      int64 total_size,
-                     bool get_attached_images)
+                     bool get_attached_images,
+                     MediaDataSource media_data_source)
       => (bool parse_success,
           mojo.common.mojom.DictionaryValue metadata,
           array<AttachedImage> attached_images);
 
   // Validate the passed media file with sanity checks, and file decoding
   // for at most |decode_time| wall clock time. Returns |success| true if
   // |file| appears to be a well-formed media file, false otherwise.
   // Note: it is still not safe to decode the file in the browser process
   // after this check.
   CheckMediaFile(mojo.common.mojom.TimeDelta decode_time,
                  mojo.common.mojom.File file)
       => (bool success);
 };
+
+interface MediaDataSource {
+  // ParseMediaMetadata interface used to read blob data for parsing from
+  // the browser process.
+  ReadBlob(int64 request_id, int64 position, int64 length)

[Sam McNally, 2017/02/03 22:14:16]

Remove |request_id|.

[Noel Gordon, 2017/02/05 23:45:03]

Indeed, done.

+      => (int64 request_id, array<uint8> data);
+};
+
+struct AttachedImage {
+  // If ParseMediaMetadata returns attached images, each of the images is
+  // returned in an AttachedImage object.
+  string type;
+  array<uint8> data;
+};