Motown: Get rid of speculative clock definition

mojo/services/media/common/interfaces/media_clock.mojom

-// Copyright 2015 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.
-
-[DartPackage="mojo_services"]
-module mojo.media;
-
-// Expresses a component's disposition with respect to being a clock master or
-// slave.
-enum ClockDisposition {
-  // Clocks are irrelevant. Component will produce/consume on demand.
-  PASSIVE,
-
-  // Component must slave to a master clock.
-  SLAVE,
-
-  // Component can be master or slave, but being slave is preferred.
-  PREFER_SLAVE,
-
-  // Component can be master or slave, doesn't care which.
-  INDIFFERENT,
-
-  // Component can be master or slave, but master is preferred.
-  PREFER_MASTER,
-
-  // Component must be master and cannot slave to a master clock.
-  MASTER,
-};
-
-interface Clock {
-  // TODO(dalesat): Define this.
-};