Add the copresence DirectiveHandler.

components/copresence/public/copresence_constants.h

+// Copyright 2014 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 COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_CONSTANTS_
+#define COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_CONSTANTS_
+
+#include "media/base/channel_layout.h"
+
+namespace copresence {
+
+// Audio constants. Currently used from the AudioPlayer/AudioRecorder.

[Daniel Erat, 2014/07/31 22:31:16]

does this really need to be in the public/ subdirectory? this comment indicates
that these are internal constants.

[rkc, 2014/08/01 21:08:57]

They are shared by the whispernet implementation (see
https://codereview.chromium.org/438513002/)

+// TODO(rkc): Make these values configurable then remove them from here.
+// Number of repetitions of the audio token in one sequence of samples.
+extern const int kDefaultRepetitions;

[Daniel Erat, 2014/07/31 22:31:16]

add a blank line between this one and the next one, and similarly between
following variables

[rkc, 2014/08/01 21:08:57]

Done.

+// The default sample rate. We need to ensure that both the recorder and the
+// player on _all platforms use the same rate.
+extern const float kDefaultSampleRate;
+extern const int kDefaultBitsPerSample;
+// 18500 for ultrasound, needs to be consistent between platforms.
+extern const float kDefaultCarrierFrequency;
+// The next two really need to be configurable since they don't need to be
+// consistent across platforms, or even playing/recording.
+extern const int kDefaultChannels;
+extern const media::ChannelLayout kDefaultChannelLayout;
+
+}  // namespace copresence
+
+#endif  // COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_CONSTANTS_