[ios] Adds a provider API for AudioSessionController.

ios/chrome/browser/voice/test_audio_session_controller.cc

Index: ios/chrome/browser/voice/test_audio_session_controller.cc
diff --git a/ios/chrome/browser/voice/test_audio_session_controller.cc b/ios/chrome/browser/voice/test_audio_session_controller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..85f2dc2bdddf33f94b650498b55a07ce85c8ea7f
--- /dev/null
+++ b/ios/chrome/browser/voice/test_audio_session_controller.cc
@@ -0,0 +1,15 @@
+// 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.
+
+#include "ios/chrome/browser/voice/test_audio_session_controller.h"
+
+#include "base/logging.h"
+
+void TestAudioSessionController::InitializeSessionIfNecessary() {}
+
+AudioSessionMode TestAudioSessionController::GetSessionMode() {
+  return AudioSessionMode::PLAYBACK;
+}
+
+void TestAudioSessionController::SetSessionMode(AudioSessionMode mode) {}