[ios] Adds VoiceSearchBar creation methods to VoiceSearchProvider.

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 98890042ad367dd0ee36a524dc41d51d86700ff1..3391e10350882aee9c0e83a8cc3c1b1983baaee2 100644
--- a/ios/public/provider/chrome/browser/voice/voice_search_provider.h
+++ b/ios/public/provider/chrome/browser/voice/voice_search_provider.h
@@ -6,11 +6,13 @@
 #define IOS_PUBLIC_PROVIDER_CHROME_BROWSER_VOICE_VOICE_SEARCH_PROVIDER_H_
 
 #include <Foundation/Foundation.h>
+#include <UIKit/UIKit.h>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 
 class AudioSessionController;
+@protocol VoiceSearchBar;
 class VoiceSearchController;
 
 namespace ios {
@@ -34,6 +36,10 @@ class VoiceSearchProvider {
   virtual scoped_refptr<VoiceSearchController> CreateVoiceSearchController(
       ios::ChromeBrowserState* browser_state) const;
 
+  // Creates a new VoiceSearchBar.  The caller assumes ownership.
+  virtual UIView<VoiceSearchBar>* CreateVoiceSearchBar(CGRect frame) const
+      NS_RETURNS_RETAINED;

[kkhorimoto, 2016/10/27 17:22:47]

is NS_RETURNS_RETAINED an ARC-related annotation?  It might be worthwhile
sending out a PSA on when to use these for interfacing between C++ and ARC code

[rohitrao (ping after 24h), 2016/10/27 17:47:28]

I've been cargo-culting it.  Will check with stk about sending out a PSA.  I
think it's helpful for him as he manually migrates files, but it may not
directly affect correctness?

+
  private:
   DISALLOW_COPY_AND_ASSIGN(VoiceSearchProvider);
 };