[ios] Adds a provider API for AudioSessionController.

ios/public/provider/chrome/browser/voice/voice_search_provider.mm

Index: ios/public/provider/chrome/browser/voice/voice_search_provider.mm
diff --git a/ios/public/provider/chrome/browser/voice/voice_search_provider.mm b/ios/public/provider/chrome/browser/voice/voice_search_provider.mm
new file mode 100644
index 0000000000000000000000000000000000000000..45f175280218419b1e4b46c4218821cac5275214
--- /dev/null
+++ b/ios/public/provider/chrome/browser/voice/voice_search_provider.mm
@@ -0,0 +1,13 @@
+// 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.
+
+#import "ios/public/provider/chrome/browser/voice/voice_search_provider.h"
+
+NSArray* VoiceSearchProvider::GetAvailableLanguages() const {
+  return @[];
+}
+
+AudioSessionController* VoiceSearchProvider::GetAudioSessionController() const {
+  return nil;
+}