[ios] Adds a provider API for AudioSessionController.

ios/public/provider/chrome/browser/voice/audio_session_controller.h

+// 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.
+
+#ifndef IOS_PUBLIC_PROVIDER_CHROME_BROWSER_VOICE_AUDIO_SESSION_CONTROLLER_H_
+#define IOS_PUBLIC_PROVIDER_CHROME_BROWSER_VOICE_AUDIO_SESSION_CONTROLLER_H_
+
+#include "base/macros.h"
+
+// The modes in which the audio session can be configured.
+enum class AudioSessionMode : bool { PLAYBACK, RECORDING };
+
+class AudioSessionController {
+ public:
+  AudioSessionController() = default;
+  virtual ~AudioSessionController() = default;
+
+  // Initializes the audio session for the current audio session mode.
+  virtual void InitializeSessionIfNecessary() = 0;
+
+  // Getter and setter for the audio session mode.  Setting to a new value will
+  // configure the audio session for that mode.
+  virtual AudioSessionMode GetSessionMode() = 0;
+  virtual void SetSessionMode(AudioSessionMode mode) = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AudioSessionController);
+};
+
+#endif  // IOS_PUBLIC_PROVIDER_CHROME_BROWSER_VOICE_AUDIO_SESSION_CONTROLLER_H_