Standardize usage of virtual/override/final in content/

content/test/test_content_client.h

Index: content/test/test_content_client.h
diff --git a/content/test/test_content_client.h b/content/test/test_content_client.h
index 9ae7d3b13ef32a01bf1d6da85d988018bdb0ac26..2e12d4ab76324dfba5eb3298c7124b1127174276 100644
--- a/content/test/test_content_client.h
+++ b/content/test/test_content_client.h
@@ -17,11 +17,11 @@ namespace content {
 class TestContentClient : public ContentClient {
  public:
   TestContentClient();
-  virtual ~TestContentClient();
+  ~TestContentClient() override;
 
   // ContentClient:
-  virtual std::string GetUserAgent() const override;
-  virtual base::StringPiece GetDataResource(
+  std::string GetUserAgent() const override;
+  base::StringPiece GetDataResource(
       int resource_id,
       ui::ScaleFactor scale_factor) const override;