Warn on missing OVERRIDE/virtual everywhere, not just in header files.

ash/shell/app_list.cc

Index: ash/shell/app_list.cc
diff --git a/ash/shell/app_list.cc b/ash/shell/app_list.cc
index 9afee4fab169001a8c79ef906f0b7ad837c04232..7ee4d388b1cd2f87d90109dd9815ebb403f5697d 100644
--- a/ash/shell/app_list.cc
+++ b/ash/shell/app_list.cc
@@ -295,19 +295,19 @@ class ExampleAppListViewDelegate : public app_list::AppListViewDelegate {
     return gfx::ImageSkia();
   }
 
-  virtual base::string16 GetCurrentUserName() {
+  virtual base::string16 GetCurrentUserName() OVERRIDE {
     return base::string16();
   }
 
-  virtual base::string16 GetCurrentUserEmail() {
+  virtual base::string16 GetCurrentUserEmail() OVERRIDE {
     return base::string16();
   }
 
-  virtual void OpenSettings() {
+  virtual void OpenSettings() OVERRIDE {
     // Nothing needs to be done.
   }
 
-  virtual void OpenFeedback() {
+  virtual void OpenFeedback() OVERRIDE {
     // Nothing needs to be done.
   }