Standardize usage of virtual/override/final in content/renderer/

This patch was automatically generated by applying clang fixit hints
generated by the plugin to the source tree.

BUG=417463
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Review URL: https://codereview.chromium.org/670683003

Cr-Commit-Position: refs/heads/master@{#300473}
diff --git a/content/renderer/gpu/queue_message_swap_promise.h b/content/renderer/gpu/queue_message_swap_promise.h
index 0f4ea1d..4094b1b 100644
--- a/content/renderer/gpu/queue_message_swap_promise.h
+++ b/content/renderer/gpu/queue_message_swap_promise.h
@@ -23,13 +23,13 @@
                           scoped_refptr<FrameSwapMessageQueue> message_queue,
                           int source_frame_number);
 
-  virtual ~QueueMessageSwapPromise();
+  ~QueueMessageSwapPromise() override;
 
-  virtual void DidSwap(cc::CompositorFrameMetadata* metadata) override;
+  void DidSwap(cc::CompositorFrameMetadata* metadata) override;
 
-  virtual void DidNotSwap(DidNotSwapReason reason) override;
+  void DidNotSwap(DidNotSwapReason reason) override;
 
-  virtual int64 TraceId() const override;
+  int64 TraceId() const override;
 
  private:
   void PromiseCompleted();