Cleanup: Return additional schemes vector as out parameter from GetAdditionalWebUISchemes

content/public/browser/content_browser_client.h

Index: content/public/browser/content_browser_client.h
diff --git a/content/public/browser/content_browser_client.h b/content/public/browser/content_browser_client.h
index f7e520066f5f38347d93497f46c155a743cd6e23..0c417e90f7771ad50694d3fb35a9dd29774ca8a3 100644
--- a/content/public/browser/content_browser_client.h
+++ b/content/public/browser/content_browser_client.h
@@ -151,7 +151,8 @@ class CONTENT_EXPORT ContentBrowserClient {
   // act as aliases to the chrome: scheme.  The additional schemes may or may
   // not serve specific WebUI pages depending on the particular URLDataSource
   // and its override of URLDataSource::ShouldServiceRequest.
-  virtual std::vector<std::string> GetAdditionalWebUISchemes();
+  virtual void GetAdditionalWebUISchemes(
+      std::vector<std::string>* additional_schemes) {}
 
   // Creates the main net::URLRequestContextGetter. Should only be called once
   // per ContentBrowserClient object.