[ios] Adds a VoiceSearchController interface to the provider layer.

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

Index: ios/public/provider/chrome/browser/voice/voice_search_provider.h
diff --git a/ios/public/provider/chrome/browser/voice/voice_search_provider.h b/ios/public/provider/chrome/browser/voice/voice_search_provider.h
index 248f6c241d2a537378443821aaeab9f8ab5ae4c3..560fb2e0023736059bda803dd0efb29a6aabba37 100644
--- a/ios/public/provider/chrome/browser/voice/voice_search_provider.h
+++ b/ios/public/provider/chrome/browser/voice/voice_search_provider.h
@@ -10,6 +10,11 @@
 #include "base/macros.h"
 
 class AudioSessionController;
+class VoiceSearchController;
+
+namespace ios {
+class ChromeBrowserState;
+}
 
 // VoiceSearchProvider allows embedders to provide functionality related to
 // voice search.
@@ -24,6 +29,10 @@ class VoiceSearchProvider {
   // Returns the singleton audio session controller.
   virtual AudioSessionController* GetAudioSessionController() const;
 
+  // Creates a new VoiceSearchController object.
+  virtual VoiceSearchController* CreateVoiceSearchController(
+      ios::ChromeBrowserState* browser_state) const;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(VoiceSearchProvider);
 };