Remove usage of FOR_EACH_OBSERVER macro in ash/common

ash/common/shelf/shelf_button.cc

Index: ash/common/shelf/shelf_button.cc
diff --git a/ash/common/shelf/shelf_button.cc b/ash/common/shelf/shelf_button.cc
index cb23ecd417ad17a9f56475476973c142ffabbbc2..ef00082ce3f6de53770d4df141be23cdd5b58971 100644
--- a/ash/common/shelf/shelf_button.cc
+++ b/ash/common/shelf/shelf_button.cc
@@ -121,7 +121,8 @@ class ShelfButtonAnimation : public gfx::AnimationDelegate {
       return;
     if (!animation_.is_animating())
       return;
-    FOR_EACH_OBSERVER(Observer, observers_, AnimationProgressed());
+    for (auto& observer : observers_)
+      observer.AnimationProgressed();
   }
 
   gfx::ThrobAnimation animation_;