Standardize usage of virtual/override/final in ui/

ui/gl/gl_context_stub_with_extensions.h

Index: ui/gl/gl_context_stub_with_extensions.h
diff --git a/ui/gl/gl_context_stub_with_extensions.h b/ui/gl/gl_context_stub_with_extensions.h
index e701e0d40541b83d5c11d91b57b3ee87cceaa4bf..190e03efad3cd3a30c8cf2538bd81621d797450d 100644
--- a/ui/gl/gl_context_stub_with_extensions.h
+++ b/ui/gl/gl_context_stub_with_extensions.h
@@ -15,15 +15,15 @@ namespace gfx {
 class GL_EXPORT GLContextStubWithExtensions : public gfx::GLContextStub {
  public:
   GLContextStubWithExtensions() {}
-  virtual std::string GetExtensions() override;
+  std::string GetExtensions() override;
 
   void AddExtensionsString(const char* extensions);
   void SetGLVersionString(const char* version_str);
 
  protected:
-  virtual std::string GetGLVersion() override;
+  std::string GetGLVersion() override;
 
-  virtual ~GLContextStubWithExtensions() {}
+  ~GLContextStubWithExtensions() override {}
 
  private:
   std::string extensions_;