replace OVERRIDE and FINAL with override and final in base/

base/process/kill_posix.cc

Index: base/process/kill_posix.cc
diff --git a/base/process/kill_posix.cc b/base/process/kill_posix.cc
index adc1db31c31e7773ce819564320fa2650e5187d6..d4ca72696bf0f664cd33d04ea2f6cf3437d6ec3d 100644
--- a/base/process/kill_posix.cc
+++ b/base/process/kill_posix.cc
@@ -410,7 +410,7 @@ class BackgroundReaper : public PlatformThread::Delegate {
   }
 
   // Overridden from PlatformThread::Delegate:
-  virtual void ThreadMain() OVERRIDE {
+  virtual void ThreadMain() override {
     WaitForChildToDie();
     delete this;
   }