Standardize usage of virtual/override/final in gpu/

gpu/config/gpu_test_config.h

Index: gpu/config/gpu_test_config.h
diff --git a/gpu/config/gpu_test_config.h b/gpu/config/gpu_test_config.h
index 8600a4ae4418c3506a029b69b80d68299a4d12e2..b83e027a2c83db6b4180a444f70eb6ed86d41433 100644
--- a/gpu/config/gpu_test_config.h
+++ b/gpu/config/gpu_test_config.h
@@ -92,10 +92,10 @@ class GPU_EXPORT GPUTestConfig {
 class GPU_EXPORT GPUTestBotConfig : public GPUTestConfig {
  public:
   GPUTestBotConfig() { }
-  virtual ~GPUTestBotConfig();
+  ~GPUTestBotConfig() override;
 
   // This should only be called when no gpu_vendor is added.
-  virtual void AddGPUVendor(uint32 gpu_vendor) override;
+  void AddGPUVendor(uint32 gpu_vendor) override;
 
   // Return false if gpu_info does not have valid vendor_id and device_id.
   bool SetGPUInfo(const GPUInfo& gpu_info);
@@ -103,7 +103,7 @@ class GPU_EXPORT GPUTestBotConfig : public GPUTestConfig {
   // Check if the bot config is valid, i.e., if it is one valid test-bot
   // environment. For example, if a field is unknown, or if OS is not one
   // fully defined OS, then it's valid.
-  virtual bool IsValid() const override;
+  bool IsValid() const override;
 
   // Check if a bot config matches a test config, i.e., the test config is a
   // superset of the bot config.