Global Resource Coordinator: Basic service internals

services/resource_coordinator/public/interfaces/coordination_unit.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.
+
+module resource_coordinator.mojom;
+
+import "events.mojom";
+
+// Any new type here needs to be mirrored between coordination_unit_types.h and
+// coordination_unit.mojom, and have mappings between the two defined in
+// coordination_unit_struct_traits.h/.cc

[nasko, 2017/04/21 00:17:32]

Add a short note as to why this type is duplicated in coordination_unit_types.h
as well.

[oystein (OOO til 10th of July), 2017/04/21 17:57:55]

Done.

+enum CoordinationUnitType {
+  WEBCONTENTS,

[nasko, 2017/04/21 00:17:32]

nit: Maybe start moving to k-prefixed enum values as per
https://groups.google.com/a/chromium.org/d/msg/chromium-dev/5AqwVQt-Etg/pBDaP...
Otherwise, WEB_CONTENTS is a bit more readable.

[oystein (OOO til 10th of July), 2017/04/21 17:57:55]

Ah, great. Done. I much prefer the k-prefixed version anyway :).

+  FRAME,
+  NAVIGATION,
+  PROCESS,
+};
+
+struct CoordinationUnitID {
+  CoordinationUnitType type;
+  int32 id;

[nasko, 2017/04/21 00:17:32]

Would 32bits be good enough for very long lived browser session? A web page can
very easily spam with a pushState() in a tight loop, which is technically
considered a navigation. If we attach an ID to each one of those, attackers can
potentially cause an overflow.

[oystein (OOO til 10th of July), 2017/04/21 17:57:55]

Probably better to err on the side of safety here, so I'm fine with 64bits. We
can re-evaluate if we start using CUIDs at a low enough level of granularity
that it becomes an issue. Done.

+};
+
+struct Policy {
+  bool use_background_priority;
+};
+
+interface PolicyCallback {
+  SetPolicy(Policy policy);
+};
+
+interface CoordinationUnit {
+  SendEvent(Event event);
+
+  // Mainly used to force a round-trip to the service over the pipe for
+  // a specific unit, so we don't have to deal with possibly-not-yet-created
+  // children in AddChild()
+  GetID() => (CoordinationUnitID id);

[Ken Rockot(use gerrit already), 2017/04/18 21:56:54]

I guess this is fine for now (a Ping() => () would be just as reasonable IMHO).
I wonder if we should just add a common async Flush method to all InterfacePtrs.

+
+  Duplicate(CoordinationUnit& request);
+  AddChild(CoordinationUnitID child_id);
+  SetPolicyCallback(PolicyCallback callback);
+};