Add virtual and OVERRIDE to base/ implementation files

base/metrics/stats_table_unittest.cc

Index: base/metrics/stats_table_unittest.cc
diff --git a/base/metrics/stats_table_unittest.cc b/base/metrics/stats_table_unittest.cc
index 447769cf029258eb424d5c7914e4c70a927214d4..62a5839c7ce5946eac313510b9c950622d47fca3 100644
--- a/base/metrics/stats_table_unittest.cc
+++ b/base/metrics/stats_table_unittest.cc
@@ -76,8 +76,10 @@ class StatsTableThread : public SimpleThread {
  public:
   StatsTableThread(std::string name, int id)
       : SimpleThread(name),
-      id_(id) {}
-  virtual void Run();
+        id_(id) {}
+
+  virtual void Run() OVERRIDE;
+
  private:
   int id_;
 };