Standardize usage of virtual/override/final in gpu/

gpu/command_buffer/service/gpu_state_tracer.cc

Index: gpu/command_buffer/service/gpu_state_tracer.cc
diff --git a/gpu/command_buffer/service/gpu_state_tracer.cc b/gpu/command_buffer/service/gpu_state_tracer.cc
index 5311e9cc8c40dbac46dd0a5579480677bf646ffa..51b0eba141fbcc5ac792082bc9d7f8f2c8f22081 100644
--- a/gpu/command_buffer/service/gpu_state_tracer.cc
+++ b/gpu/command_buffer/service/gpu_state_tracer.cc
@@ -24,11 +24,11 @@ class Snapshot : public base::debug::ConvertableToTraceFormat {
   bool SaveScreenshot(const gfx::Size& size);
 
   // base::debug::ConvertableToTraceFormat implementation.
-  virtual void AppendAsTraceFormat(std::string* out) const override;
+  void AppendAsTraceFormat(std::string* out) const override;
 
  private:
   explicit Snapshot(const ContextState* state);
-  virtual ~Snapshot() {}
+  ~Snapshot() override {}
 
   const ContextState* state_;