[chromium-discuss] How can i create a button in toolbar like App Menu Button

[Long Le]

I want to create a new button in the toolbar and when i click on it, it
will show a view like this

[image: neater-bookmarks-installed.png]
Where should i start with this? I know there are some bookmark extensions
can do this but i want to do it in the code base with C++, build it
directly to chromium on start.
I had take a look at App Menu Button
<https://cs.chromium.org/chromium/src/chrome/browser/ui/views/frame/app_menu_button.h>,
but im not good at read the code and figure out the solution by myself. Can
i have some advices for this?