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

ash/launcher/launcher_button.cc

Index: ash/launcher/launcher_button.cc
diff --git a/ash/launcher/launcher_button.cc b/ash/launcher/launcher_button.cc
index dad5d18cedf127215197508ed084deccee9d0a9c..78fc815784842909526cd95331ebe9bc74ef1397 100644
--- a/ash/launcher/launcher_button.cc
+++ b/ash/launcher/launcher_button.cc
@@ -96,7 +96,7 @@ class LauncherButtonAnimation : public ui::AnimationDelegate {
   }
 
   // ui::AnimationDelegate
-  void AnimationProgressed(const ui::Animation* animation) {
+  virtual void AnimationProgressed(const ui::Animation* animation) OVERRIDE {
     if (animation != &animation_)
       return;
     if (!animation_.is_animating())
@@ -126,7 +126,7 @@ class LauncherButton::BarView : public views::ImageView,
         show_attention_(false) {
   }
 
-  ~BarView() {
+  virtual ~BarView() {
     if (show_attention_)
       LauncherButtonAnimation::GetInstance()->RemoveObserver(this);
   }