Able to reproduce this issue on Ubuntu 14.04 using chrome latest dev #60.0.3104.0. This issue is not observed on Mac OS 10.12.

NOTE: One more issue is seen
1. Zoom in/Zoo out and now make zoom level as 100 and observe zoom bubble

Expected: No zoom bubble should be seen when zoom is 100.
Actual:Instead zoom bubble is seen for 100% zoom as well

 Issue 724388  has been merged into this issue.

Using the per-revision bisect providing the bisect results,
Good build: 60.0.3103.0 (Revision: 472587).
Bad build : 60.0.3104.0 (Revision: 473014).

You are probably looking for a change made after 472890 (known good), but no later than 472891 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/89c24d4a46c1f0e7ad03891a659e6d23dc776c36..f6f47b5a77854b023c3ccd6c57d1584051f2280a

@varkha: Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to concern owner.
Adding RB Label as this is a recent Regression. Please remove if not required.
Thank You.

Overall this seems WAI after r472891.

With the zoom dialog changed to have + and - buttons in the bubble it no longer made sense to special-case the reset button to close the dialog immediately. All buttons now behave the same when clicked - resetting the auto-close timeout and giving a user another 5 seconds to not have the bubble auto-close. Additionally (unchanged from before) as long as the mouse pointer is within the bubble auto-close is deferred.
I believe if the actial_zoom video above were to extend a couple seconds more the bubble would have auto-closed as long as the mouse pointer was not within the bubble (5 seconds after the button click).

Marking other desktop platforms since this behavior is universal with --secondary-ui-md flag enabled.

varkha, I notice you didn't close the bug, but you did say "seems WAI" (which I agree with).

What do you perceive as the work to be done here, if any?

#11, no, I just wanted to give it a few hours to let everybody digest and check. I will mark it WontFix now. Please reopen if you feel this needs more work.

NOTE: Even after 5 seconds bubble doesn't get closed on hitting reset button through space/enter

Once the bubble closes after zoom in/out and reopening bubble and resetting doesn't make zoom bubble vanish

Steps: Hit Ctrl+ +/- to zoom in/out and leave it so that zoom bubble vanishes >> Now click on zoom bubble again using mouse/focus using keyboard, Hit reset button and observe

Expected: Bubble should vanish after 5 seconds
Actual: Instead bubble remains and doesn't get closed even after 5 secs. Only clicking outside bubble closes it.

@Varkha: Please find the above steps and feel free to close it if it working as Intended.

Yes, thanks for checking. I think this is WAI. If a dialog is opened by a user action it doesn't auto-close. We could auto-close in fact on Reset but I think it would be double-guessing user intent a bit.