ImageCapture: introduce image_capture Blob to allow move-only semantics

media/mojo/interfaces/image_capture.mojom

 // 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.
 
 module media.mojom;
 
 // Equivalent to idl MediaSettingsRange, arbitrary range representing the
 // allowed variations of a Capability or an Option.
 // https://w3c.github.io/mediacapture-image/#mediasettingsrange
 struct Range {
@@ skipping 20 matching lines @@
 struct PhotoSettings {
   // uint32 cannot be nullable, i.e. uint32? does not work, use instead a flag.
   bool has_zoom;
   uint32 zoom;
   bool has_width;
   uint32 width;
   bool has_height;
   uint32 height;
 };
 
+// This is a mojo move-only equivalent of a Blob, i.e. MIME type and Data.
+struct Blob {
+  string mime_type;
+  array<uint8> data;
+};
+
 // |source_id| is the renderer-side UUID identifier of the image capture device.
 interface ImageCapture
 {
     // Retrieves the image capture device capabilities and current settings.
     // https://w3c.github.io/mediacapture-image/index.html#widl-ImageCapture-getPhotoCapabilities-Promise-PhotoCapabilities
     GetCapabilities(string source_id)
         => (PhotoCapabilities capabilities);
 
     // Sets the |settings| on the associated video capture device.
     // https://w3c.github.io/mediacapture-image/index.html#widl-ImageCapture-setOptions-Promise-void--PhotoSettings-photoSettings
     SetOptions(string source_id, PhotoSettings settings)
         => (bool success);
 
-    // Takes a Photo from the given |source_id|, returning it encoded in |data|
-    // with the format specified in |mime_type|.
+    // Takes a Photo from the given |source_id|, returning it encoded in |blob|
+    // with the format specified in its |mime_type|.
     // https://w3c.github.io/mediacapture-image/index.html#widl-ImageCapture-takePhoto-Promise-Blob
     TakePhoto(string source_id)
-        => (string mime_type, array<uint8> data);
+        => (Blob blob);
 };