Fix memory management of VoiceSearchBarView.

The VoiceSearchProvider is written in ARC, so the returned value is
autoreleased despite the function having "Created" in the name.  This
CL correctly retains the returned value to prevent over-releasing the
view.

BUG=679719

Review-Url: https://codereview.chromium.org/2644703003
Cr-Commit-Position: refs/heads/master@{#445769}

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

@@ -41,9 +41,14 @@ class VoiceSearchProvider {
       ios::ChromeBrowserState* browser_state) const;
 
   // Creates a new VoiceSearchBar.  The caller assumes ownership.
+  // TODO(crbug.com/679719): Remove this once downstream provider implementaiton
+  // switches to BuildVoiceSearchBar().
   virtual UIView<VoiceSearchBar>* CreateVoiceSearchBar(CGRect frame) const
       NS_RETURNS_RETAINED;
 
+  // Creates a new VoiceSearchBar.  Returns an autoreleased view.
+  virtual UIView<VoiceSearchBar>* BuildVoiceSearchBar(CGRect frame) const;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(VoiceSearchProvider);
 };

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

@@ -28,3 +28,8 @@
     CGRect frame) const {
   return nil;
 }
+
+UIView<VoiceSearchBar>* VoiceSearchProvider::BuildVoiceSearchBar(
+    CGRect frame) const {
+  return nil;
+}