Standardize usage of virtual/override/final in net/

net/disk_cache/backend_unittest.cc

Index: net/disk_cache/backend_unittest.cc
diff --git a/net/disk_cache/backend_unittest.cc b/net/disk_cache/backend_unittest.cc
index b3b80b493ada45fb95c1fe44a78d2fa18073d7e6..e06efd953fa7a47eac5f1560c214b07b620f5dda 100644
--- a/net/disk_cache/backend_unittest.cc
+++ b/net/disk_cache/backend_unittest.cc
@@ -1840,10 +1840,10 @@ TEST_F(DiskCacheTest, WrongVersion) {
 
 class BadEntropyProvider : public base::FieldTrial::EntropyProvider {
  public:
-  virtual ~BadEntropyProvider() {}
+  ~BadEntropyProvider() override {}
 
-  virtual double GetEntropyForTrial(const std::string& trial_name,
-                                    uint32 randomization_seed) const override {
+  double GetEntropyForTrial(const std::string& trial_name,
+                            uint32 randomization_seed) const override {
     return 0.5;
   }
 };