Add AndroidVideoSurfaceChooser to manage overlays.

media/gpu/avda_overlay_helper.h

+// 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.
+
+#ifndef MEDIA_GPU_AVDA_OVERLAY_HELPER_H_
+#define MEDIA_GPU_AVDA_OVERLAY_HELPER_H_
+
+#include "base/bind.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "media/base/android/android_overlay.h"
+#include "media/base/android/android_overlay_factory.h"
+#include "media/gpu/media_gpu_export.h"
+
+namespace media {
+
+// Manage details of which overlay to use for video playback, if any.
+class MEDIA_GPU_EXPORT AVDAOverlayHelper {

[watk, 2017/04/27 20:33:10]

Can we replace Helper with a word that indicates the purpose of this thing?
OverlayCoordinator, OverlayScheduler, OverlayTransitionScheduler,
OverlayTransitionCoordinator, OverlayChooser

Actually I kinda like using Surface instead of overlay. Because both STs and
Overlays are Surfaces: SurfaceSelector, SurfaceCoordinator, etc.

[liberato (no reviews please), 2017/04/27 21:31:44]

AndroidVideoSurfaceChooser .  Also gets rid of AVDA, since hopefully this is
useful for MCVD.

+ public:
+  // Notify the client that |overlay| is ready for use.  The client may get
+  // the surface immediately.
+  using UseOverlayCB =
+      base::Callback<void(std::unique_ptr<AndroidOverlay> overlay)>;
+
+  // Notify the client that the most recently provided overlay should be
+  // discarded.  The overlay is still valid, but we recommend against
+  // using it soon, in favor of a SurfaceTexture.
+  using UseSurfaceTextureCB = base::Callback<void(void)>;
+
+  // Callback that mirrors AndroidOverlay::DestroyedCB .  The surface
+  // that was provided with |overlay| is being destroyed.
+  using StopUsingOverlayImmediatelyCB = base::Callback<void(AndroidOverlay*)>;
+
+  AVDAOverlayHelper() {}
+  virtual ~AVDAOverlayHelper() {}
+
+  // Notify us that our client is ready for overlays.  We will send it a
+  // callback telling it whether to start with a SurfaceTexture or overlay,
+  // either synchronously or post one very soon.
+  virtual void Initialize(
+      const UseOverlayCB& use_overlay_cb,
+      const UseSurfaceTextureCB& use_surface_texture_cb,
+      const StopUsingOverlayImmediatelyCB& stop_immediately_cb,
+      std::unique_ptr<AndroidOverlayFactory> initial_factory) = 0;
+
+  // Notify us that a new factory has arrived.  May be null to indicate that
+  // WMPI has revoked the most recent factory.
+  virtual void OnOverlayFactory(

[watk, 2017/04/27 20:33:10]

Name sounds weird to me. What about just SetOverlayFactory()? Or if you want the
"On", I would prefer OnOverlayFactoryChanged().

+      std::unique_ptr<AndroidOverlayFactory> factory) = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AVDAOverlayHelper);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_GPU_AVDA_OVERLAY_HELPER_H_