[ios] Adds a provider API for AudioSessionController.

ios/public/provider/chrome/browser/voice/voice_search_provider.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_VOICE_SEARCH_PROVIDER_H_
+#define IOS_PUBLIC_PROVIDER_CHROME_BROWSER_VOICE_VOICE_SEARCH_PROVIDER_H_
+
+#include <Foundation/Foundation.h>
+
+#include "base/macros.h"
+
+class AudioSessionController;
+
+// VoiceSearchProvider allows embedders to provide functionality related to
+// voice search.
+class VoiceSearchProvider {
+ public:
+  VoiceSearchProvider() = default;
+  virtual ~VoiceSearchProvider() = default;
+
+  // Returns the list of available voice search languages.
+  virtual NSArray* GetAvailableLanguages() const;
+
+  // Returns the singleton audio session controller.
+  virtual AudioSessionController* GetAudioSessionController() const;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(VoiceSearchProvider);
+};
+
+#endif  // IOS_PUBLIC_PROVIDER_CHROME_BROWSER_VOICE_VOICE_SEARCH_PROVIDER_H_