[Mac] App Menu Animated Icon

chrome/browser/ui/cocoa/menu_button.mm

Index: chrome/browser/ui/cocoa/menu_button.mm
diff --git a/chrome/browser/ui/cocoa/menu_button.mm b/chrome/browser/ui/cocoa/menu_button.mm
index 15ffcab3c8d1a1285bcd3312731e5c78af7b15ad..9e79a212bb40c8071fbe41bc3470c0747c901e14 100644
--- a/chrome/browser/ui/cocoa/menu_button.mm
+++ b/chrome/browser/ui/cocoa/menu_button.mm
@@ -94,6 +94,10 @@
   return [self bounds];
 }
 
+- (void)willShowMenu {
+  // Subclasses should implement this, but it's not necessary.
+}
+
 @end  // @implementation MenuButton
 
 @implementation MenuButton (Private)
@@ -179,6 +183,7 @@
                                                    pullsDown:YES]);
   }
   DCHECK(popUpCell_.get());
+  [self willShowMenu];
   [popUpCell_ setMenu:[self attachedMenu]];
   [popUpCell_ selectItem:nil];
   [popUpCell_ attachPopUpWithFrame:frame inView:self];