This is because of the logic here:

https://chromium.googlesource.com/chromium/src/+/e1f22d6dc1a522e2880d80c6abd1a55f6fe0bdd5/chrome/browser/ui/toolbar/toolbar_actions_bar.cc#635

  // If the extension is being upgraded we don't want the bar to shrink
  // because the icon is just going to get re-added to the same location.

We'd need to monitor if the extension reload fails, and adjust accordingly.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e9a2d8497e479f30472052c89ef6c23c7c13de22

commit e9a2d8497e479f30472052c89ef6c23c7c13de22
Author: Catherine Mullings <catmullings@chromium.org>
Date: Tue Nov 21 01:36:06 2017

Extensions: Remove empty toolbar slot when extension load fails

When an extension is re-uploaded, it is first unloaded from Chrome. At
this point, the extension's icon is initially removed from the toolbar,
leaving an empty slot in the toolbar. Then the (newer version of the)
extension is loaded, and its icon populates the empty slot.

If the extension failed to load, then the empty slot should be
removed.

Bug:  776994 
Change-Id: I17bcd0a600d23048a5af7554e636a80d00dfaa30

TBR=apacible@chromium.org,avi@chromium.org

Change-Id: I17bcd0a600d23048a5af7554e636a80d00dfaa30
Reviewed-on: https://chromium-review.googlesource.com/765193
Commit-Queue: catmullings <catmullings@chromium.org>
Reviewed-by: apacible <apacible@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: catmullings <catmullings@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518039}
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/extensions/extension_message_bubble_controller_unittest.cc
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/cocoa/toolbar/toolbar_controller_unittest.mm
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/toolbar/media_router_contextual_menu_unittest.cc
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/toolbar/toolbar_actions_bar.cc
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/toolbar/toolbar_actions_bar.h
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/toolbar/toolbar_actions_bar_unittest.cc
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/toolbar/toolbar_actions_model.cc
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/toolbar/toolbar_actions_model.h
[modify] https://crrev.com/e9a2d8497e479f30472052c89ef6c23c7c13de22/chrome/browser/ui/toolbar/toolbar_actions_model_unittest.cc