Remove unnecessary 'virtual' annotation from mojo

mojo/services/html_viewer/blink_url_request_type_converters.cc

Index: mojo/services/html_viewer/blink_url_request_type_converters.cc
diff --git a/mojo/services/html_viewer/blink_url_request_type_converters.cc b/mojo/services/html_viewer/blink_url_request_type_converters.cc
index 85fd796b75e98882d4c8d10a2ed45f55f5f564a4..3cae06f9420df4d7b22326ccaa7f77f9e44b56da 100644
--- a/mojo/services/html_viewer/blink_url_request_type_converters.cc
+++ b/mojo/services/html_viewer/blink_url_request_type_converters.cc
@@ -17,8 +17,8 @@ class HeaderFlattener : public blink::WebHTTPHeaderVisitor {
  public:
   HeaderFlattener() : has_accept_header_(false) {}
 
-  virtual void visitHeader(const blink::WebString& name,
-                           const blink::WebString& value) {
+  void visitHeader(const blink::WebString& name,
+                   const blink::WebString& value) override {
     // Headers are latin1.
     const std::string& name_latin1 = name.latin1();
     const std::string& value_latin1 = value.latin1();