Chrome Version: 69.0.3450.0

What steps will reproduce the problem?
(1) Install an extension that uses the tabs zoom API such as "Tabs Zoom API Demo" ( https://developer.chrome.com/extensions/samples#search:tabs%20zoom%20api%20demo )
(2) Zoom a web page via the extension
(3) Observe that the zoom bubble appears and attributes the zoom change to the extension
(4) Before the bubble closes, zoom again via the extension
(5) Observe that the zoom bubble is closed and a new bubble is created
(6) Before the bubble closes, close the extension's popup and zoom the page manually (Ctrl-+)
(7) Observe that the existing zoom bubble is reused for the manual zoom change

What is the expected result?
If an extension initiated zoom opens the zoom bubble, a subsequent zoom by the same extension should be able to reuse the zoom bubble, since the attribution is the same. Also, if a manual zoom occurs while a zoom bubble attributed to an extension is showing, the zoom bubble should not be reused.

What happens instead?
Step 5: A new zoom bubble is created for each extension initiated zoom even though a bubble with the correct attribution is already showing.
Step 7: A manual zoom is incorrectly attributed to an extension.