Get rid of some lingering MD-specific raster assets.

chrome/browser/ui/extensions/extension_action_view_controller.h

Index: chrome/browser/ui/extensions/extension_action_view_controller.h
diff --git a/chrome/browser/ui/extensions/extension_action_view_controller.h b/chrome/browser/ui/extensions/extension_action_view_controller.h
index 8430f47c4404b8006e973e6ebb31a3d803df8a61..cc2d81cdc0699af9b4866335f7bae072fc073212 100644
--- a/chrome/browser/ui/extensions/extension_action_view_controller.h
+++ b/chrome/browser/ui/extensions/extension_action_view_controller.h
@@ -86,10 +86,6 @@ class ExtensionActionViewController
   ToolbarActionViewDelegate* view_delegate() { return view_delegate_; }
   bool is_showing_popup() const { return popup_host_ != nullptr; }
 
-  void set_icon_observer(ExtensionActionIconFactory::Observer* icon_observer) {
-    icon_observer_ = icon_observer;
-  }
-
   std::unique_ptr<IconWithBadgeImageSource> GetIconImageSourceForTesting(
       content::WebContents* web_contents,
       const gfx::Size& size);
@@ -185,10 +181,6 @@ class ExtensionActionViewController
   // updates to the icon.
   ExtensionActionIconFactory icon_factory_;
 
-  // An additional observer that we need to notify when the icon of the button
-  // has been updated.
-  ExtensionActionIconFactory::Observer* icon_observer_;
-
   // The associated ExtensionRegistry; cached for quick checking.
   extensions::ExtensionRegistry* extension_registry_;