Add virtual and OVERRIDE to base/ implementation files

base/threading/thread_checker_unittest.cc

Index: base/threading/thread_checker_unittest.cc
diff --git a/base/threading/thread_checker_unittest.cc b/base/threading/thread_checker_unittest.cc
index 1760cd098fa70c401b2bfdbb319f8af592f0c845..0dadcf01f0e8ddaa3fc85540ce5826f561902452 100644
--- a/base/threading/thread_checker_unittest.cc
+++ b/base/threading/thread_checker_unittest.cc
@@ -46,7 +46,7 @@ class CallDoStuffOnThread : public base::SimpleThread {
         thread_checker_class_(thread_checker_class) {
   }
 
-  virtual void Run() {
+  virtual void Run() OVERRIDE {
     thread_checker_class_->DoStuff();
   }
 
@@ -64,7 +64,7 @@ class DeleteThreadCheckerClassOnThread : public base::SimpleThread {
         thread_checker_class_(thread_checker_class) {
   }
 
-  virtual void Run() {
+  virtual void Run() OVERRIDE {
     thread_checker_class_.reset();
   }