Standardize usage of virtual/override/final in mojo/

mojo/public/cpp/bindings/tests/request_response_unittest.cc

Index: mojo/public/cpp/bindings/tests/request_response_unittest.cc
diff --git a/mojo/public/cpp/bindings/tests/request_response_unittest.cc b/mojo/public/cpp/bindings/tests/request_response_unittest.cc
index a5d562df3b9c33dbcc86019bf8ec811ed19b22af..56d7244e60939d924cb0caf2a014826abfa53727 100644
--- a/mojo/public/cpp/bindings/tests/request_response_unittest.cc
+++ b/mojo/public/cpp/bindings/tests/request_response_unittest.cc
@@ -15,29 +15,28 @@ namespace {
 
 class ProviderImpl : public InterfaceImpl<sample::Provider> {
  public:
-  virtual void EchoString(const String& a,
-                          const Callback<void(String)>& callback) override {
+  void EchoString(const String& a,
+                  const Callback<void(String)>& callback) override {
     Callback<void(String)> callback_copy;
     // Make sure operator= is used.
     callback_copy = callback;
     callback_copy.Run(a);
   }
 
-  virtual void EchoStrings(
-      const String& a,
-      const String& b,
-      const Callback<void(String, String)>& callback) override {
+  void EchoStrings(const String& a,
+                   const String& b,
+                   const Callback<void(String, String)>& callback) override {
     callback.Run(a, b);
   }
 
-  virtual void EchoMessagePipeHandle(
+  void EchoMessagePipeHandle(
       ScopedMessagePipeHandle a,
       const Callback<void(ScopedMessagePipeHandle)>& callback) override {
     callback.Run(a.Pass());
   }
 
-  virtual void EchoEnum(sample::Enum a,
-                        const Callback<void(sample::Enum)>& callback) override {
+  void EchoEnum(sample::Enum a,
+                const Callback<void(sample::Enum)>& callback) override {
     callback.Run(a);
   }
 };