Standardize usage of virtual/override/final in ui/

ui/gl/gl_osmesa_api_implementation.h

Index: ui/gl/gl_osmesa_api_implementation.h
diff --git a/ui/gl/gl_osmesa_api_implementation.h b/ui/gl/gl_osmesa_api_implementation.h
index 66f4a3496a940e156fbbf56d6a3e1c33a61fc492..9d4dbe139ae1230bc0c1e7d13f8650135bcaf28e 100644
--- a/ui/gl/gl_osmesa_api_implementation.h
+++ b/ui/gl/gl_osmesa_api_implementation.h
@@ -27,7 +27,7 @@ class GL_EXPORT OSMESAApiBase : public OSMESAApi {
 
  protected:
   OSMESAApiBase();
-  virtual ~OSMESAApiBase();
+  ~OSMESAApiBase() override;
   void InitializeBase(DriverOSMESA* driver);
 
   DriverOSMESA* driver_;
@@ -36,7 +36,7 @@ class GL_EXPORT OSMESAApiBase : public OSMESAApi {
 class GL_EXPORT RealOSMESAApi : public OSMESAApiBase {
  public:
   RealOSMESAApi();
-  virtual ~RealOSMESAApi();
+  ~RealOSMESAApi() override;
   void Initialize(DriverOSMESA* driver);
 };
 
@@ -44,7 +44,7 @@ class GL_EXPORT RealOSMESAApi : public OSMESAApiBase {
 class GL_EXPORT TraceOSMESAApi : public OSMESAApi {
  public:
   TraceOSMESAApi(OSMESAApi* osmesa_api) : osmesa_api_(osmesa_api) { }
-  virtual ~TraceOSMESAApi();
+  ~TraceOSMESAApi() override;
 
   // Include the auto-generated part of this class. We split this because
   // it means we can easily edit the non-auto generated parts right here in