Standardize usage of virtual/override/final in net/

net/base/backoff_entry_unittest.cc

Index: net/base/backoff_entry_unittest.cc
diff --git a/net/base/backoff_entry_unittest.cc b/net/base/backoff_entry_unittest.cc
index f5393e8e5663bbc40e35320008fd6f6bceca4ccc..89ec2c4d2f160c4551fc6fa7a8672528017925a1 100644
--- a/net/base/backoff_entry_unittest.cc
+++ b/net/base/backoff_entry_unittest.cc
@@ -23,11 +23,9 @@ class TestBackoffEntry : public BackoffEntry {
     SetCustomReleaseTime(TimeTicks());
   }
 
-  virtual ~TestBackoffEntry() {}
+  ~TestBackoffEntry() override {}
 
-  virtual TimeTicks ImplGetTimeNow() const override {
-    return now_;
-  }
+  TimeTicks ImplGetTimeNow() const override { return now_; }
 
   void set_now(const TimeTicks& now) {
     now_ = now;