Add PermissionDescriptor to the permissions Mojo interface.

third_party/WebKit/public/platform/modules/permissions/permission.mojom

 // Copyright 2014 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 blink.mojom;
 
 import "third_party/WebKit/public/platform/modules/permissions/permission_status.mojom";
 import "url/mojo/origin.mojom";
 
 enum PermissionName {
   GEOLOCATION,
   NOTIFICATIONS,
   PUSH_NOTIFICATIONS,
   MIDI,
-  MIDI_SYSEX,
   PROTECTED_MEDIA_IDENTIFIER,
   DURABLE_STORAGE,
   AUDIO_CAPTURE,
   VIDEO_CAPTURE,
   BACKGROUND_SYNC,
 };
 
+struct MidiPermissionDescriptor {
+  bool sysex;
+};
+
+// Union of possible extensions to the base PermissionDescriptor type.
+union PermissionDescriptorExtension {
+  MidiPermissionDescriptor midi;
+};
+
+// This struct roughly corresponds to the PermissionDescriptor dictionary as
+// defined by the Permissions API.
+struct PermissionDescriptor {
+  PermissionName name;

[ddorwin, 2016/08/24 02:43:55]

This is uninitialized.

Per my comment in the media file, an invalid enum value may be useful.

On the other hand, as noted earlier, providing a constructor that accepts a name
would be nice. This could also prevent a permission from being created without a
valid name. You'd need to make this private (possibly making the struct a
class), expose a getter, and define a constructor.

[Reilly Grant (use Gerrit), 2016/08/24 18:28:53]

This is a Mojo file. We cannot specify custom constructors.

[mlamouri (slow - plz ping), 2016/09/06 10:52:40]

Can you add an util file in Blink that would have these methods:

PermissionDescriptor createPermissionDescriptor(PermissionName);
PermissionDescriptor createMidiPermissionDescriptor(bool);

If you add this in public/, content/ should be able to access it.

[Reilly Grant (use Gerrit), 2016/09/08 22:09:52]

Unfortunately content/ can't include it because the Blink variant of the Mojo
bindings includes WTF headers. There's only one place it would be used from
content/ though (and I want to get rid of media_permission_dispatcher.cc
anyways) so it's not a big deal.

+  PermissionDescriptorExtension? extension;
+};
+
 // The Permission service provides permission handling capabilities by exposing
 // methods to check, request, and revoke permissions. It also allows a client to
 // start listening to permission changes.
 interface PermissionService {
-  HasPermission(PermissionName permission, url.mojom.Origin origin)
+  HasPermission(PermissionDescriptor permission, url.mojom.Origin origin)
     => (PermissionStatus status);
-  RequestPermission(PermissionName permission, url.mojom.Origin origin,
+  RequestPermission(PermissionDescriptor permission, url.mojom.Origin origin,
       bool user_gesture)
     => (PermissionStatus status);
-  RequestPermissions(array<PermissionName> permission, url.mojom.Origin origin,
+  RequestPermissions(array<PermissionDescriptor> permission, url.mojom.Origin origin,
       bool user_gesture)
     => (array<PermissionStatus> statuses);
-  RevokePermission(PermissionName permission, url.mojom.Origin origin)
+  RevokePermission(PermissionDescriptor permission, url.mojom.Origin origin)
     => (PermissionStatus status);
 
   // Runs the callback next time there is a permission status change for the
   // given { permission, origin }. Callers of this method will have to call it
   // again if they want to keep listening to the changes. To prevent race
   // conditions, the caller must pass the last known value.
-  GetNextPermissionChange(PermissionName permission,
+  GetNextPermissionChange(PermissionDescriptor permission,
                           url.mojom.Origin origin,
                           PermissionStatus last_known_status)
     => (PermissionStatus status);
 };