When the "Reading list" feature was added, a new menu was also added to the omnibox star:
Of course, this change upset several users who were used to clicking the star icon and quickly bookmarking the page.
Currently, if you want to remove that menu, you have to disable the "Reading list" feature entirely (with a flag), well, in Chrome Canary you can now remove the omnibox star menu and continue using the "Reading list" feature.
As it says in the commit, to remove the menu I showed above, you have to use a command line flag:
I guess this change will be enabled by default in the stable version in the future.
The command line flag also enables a new button in the Reading List bubble (this is mentioned in the commit):
PS, Everyone knows that there is a keyboard shortcut to bookmark the page, but there are users who prefer to control the device, if possible, only with the mouse (I am one of them).