Mojo framework for AndroidOverlay.

media/mojo/interfaces/android_overlay.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 media.mojom;
+
+import "media/mojo/interfaces/media_types.mojom";
+import "mojo/common/unguessable_token.mojom";
+import "ui/gfx/geometry/mojo/geometry.mojom";
+
+interface AndroidOverlayProvider {

[dcheng, 2017/03/16 08:54:25]

Also, some interface level comments that describe the high-level purpose would
be nice. I can tell by reading this CL that AndroidOverlayProvider and
AndroidOverlay live in the browser process (and are presumably used from less
privileged processes), but I'm not sure that will be so obvious a year or two
from now.

[liberato (no reviews please), 2017/03/16 16:53:53]

Done.

+  // Create an overlay and send it to |client|, using |config| as the initial
+  // configuration.  |overlay| will hold the overlay object.
+  CreateOverlay(AndroidOverlay& overlay, AndroidOverlayClient client, AndroidOverlayConfig config);
+};
+
+// One overlay instance.
+interface AndroidOverlay {
+  // Cause a layout to occur later.
+  ScheduleLayout(gfx.mojom.Rect rect);
+};
+
+// Provided by the client to receive status updates about the overlay.
+interface AndroidOverlayClient {
+  // |surface_key| is the key that can be used to retrieve the surface via
+  // binder separately.
+  OnSurfaceReady(uint64 surface_key);
+
+  // Indicates that this overlay has been permanently destroyed, or failed to
+  // initialize.  It can happen before or after OnSurfaceReady.  It will be the
+  // last callback from the overlay in any case.
+  OnDestroyed();
+};
+
+// This is not a mirror of AndroidOverlay::Config, since it contains things that
+// are specific to the mojo implementation.
+struct AndroidOverlayConfig {
+  mojo.common.mojom.UnguessableToken routing_token;

[dcheng, 2017/03/16 08:51:39]

Nit: please add some comments that describe why routing_token is necessary. In
Mojo, it's ideal to represent identity implicitly with the message pipe between
the sender and the receiver, and anytime where that isn't true, it's best to
document why that's not sufficient.

[liberato (no reviews please), 2017/03/16 16:53:53]

Done.  TL;DR: it must be sent via IPC for now.

+  gfx.mojom.Rect rect;
+};