Tabs do not automatically resize until mousing over them.

[JaneSmith]

Test plan

#10691 (comment)

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• Describe the issue you encountered:
  When opening extra tabs, all of the tabs shrink in order to make room. However, sometimes when I close the tabs via keyboard input, I notice that they do not automatically grow to fill back that space. I have to manually move my mouse over a tab to "prod them" into resizing. Once I mouse over a tab, all tabs resize to the correct dimensions.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Windows 10 Pro.

• Brave Version (revision SHA):
  36ae2ec

• Steps to reproduce:

  1. Repeatedly open a link in new tab, to get ~20 tabs. All the tabs will be quite small.
  2. Close the newest tab by clicking on its X button. With the settings set to switch to the parent tab, you will jump back to the first tab.
  3. Use Ctrl+Tab to switch tabs, closing them with Ctrl+W.

• Actual result:
  The tabs close upon pressing Ctrl+W, but the remaining tabs never resize to fill the newly available space.

• Expected result:
  The tabs close upon pressing Ctrl+W, and the remaining tabs automatically resize to fill the newly available space.

• Can this issue be consistently reproduced?
  No.