GYP->GN of audio_device_tests. Remove dead code. Fix new warnings.

webrtc/modules/audio_device/audio_device.cc

+/*
+ *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/modules/audio_device/include/audio_device.h"
+
+#include "webrtc/modules/audio_device/include/audio_device_defines.h"
+
+namespace webrtc {
+
+#if defined(WEBRTC_IOS)
+// Some AudioDeviceModule implementations do not care about these functions, so
+// we provide default implementations.
+int AudioDeviceModule::GetPlayoutAudioParameters(
+    AudioParameters* params) const {
+  return -1;
+}
+int AudioDeviceModule::GetRecordAudioParameters(AudioParameters* params) const {
+  return -1;
+}
+#endif  // WEBRTC_IOS
+}  // namespace webrtc