DialogSurfaceManager implementation.

media/base/android/java/src/org/chromium/media/DialogSurfaceWindowTokenProvider.java

+// 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.
+
+package org.chromium.media;
+
+import android.os.IBinder;
+
+/**
+ * Class to facilitate mapping (pid, render_frame_id) to an Activity.  Should
+ * also handle registering for changes if the render frame is re-parented to
+ * another activity.
+ */
+public interface DialogSurfaceWindowTokenProvider {
+    /**
+     * Client to receive callbacks from the token provider.
+     */
+    interface Client {
+        // Notify the client of a new window token, or null if no token is
+        // currently available.  This callback will happen on the UI thread.
+        void onWindowToken(IBinder token);
+    }
+
+    /**
+     * Eventually call back |client::onWindowToken| with the window token for
+     * the activity that hosts (rendererPid, renderFrameId).  This will call
+     * back, but may call back with null.  It may call back more than once if
+     * the token changes.
+     */
+    void registerClient(int rendererPid, int renderFrameId, Client client);
+
+    /**
+     * Unregister |client| for callbacks.  Some callbacks may be in-flight, and
+     * could arrive after this returns.
+     */
+    void unregisterClient(Client client);
+}