Tab size change should have transition animation

[luixxiul]

Test plan

#11438 (comment)

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Describe the issue you encountered: Tab size change after closing tabs should have animation.

• Brave Version (revision SHA): master branch

• Steps to reproduce:

  1. open 7-8 tabs (doesn't matter what the content is; can be empty)
  2. move your cursor to the close button of the second tab from left
  3. Now as you keep clicking it will maintain the size of the tabs
  4. The size will reset as soon as you move your cursor outside the tab area.

• Actual result: the size is reset without animation

• Expected result: the size should be reset with transition animation

• Extra QA steps:
  1.
  2.
  3.

• Any related issues: Keep tabs same size when closing #6088

[luixxiul]

CC @bradleyrichter for a comment

[srirambv]

Verified on Windows x64 using

• 0.23.8 06c657b
• muon 6.1.5
• libchromiumcontent 66.0.3359.181

Verified on Ubuntu 17.10 x64

• 0.23.8 06c657b
• Muon 6.1.5
• libchromiumcontent 66.0.3359.181

Verified with macOS 10.12.6 using

• 0.23.8 06c657b
• Muon 6.1.5
• libchromiumcontent 66.0.3359.181

[kjozwiak]

Once you've closed a tab and move the mouse away from the tabs toolbar, the animation doesn't trigger unless you hover over a tab that has already been created. The animation should be triggering whenever a user closes a tab and moves the cursor away from the tabs toolbar.

STR:

• open about ~15 new tabs using 0.23.11 6565c06
• close the tab that's all the way at the end of the tab toolbar and drag the mouse onto the page
• notice that the animation isn't triggered
• move the mouse over one of the already created tabs and you'll notice the animation triggering.

Example of issue:

Platforms:

• macOS 10.13.4 x64 - Reproduced using 0.23.11` 6565c06
• Win 10 x64 - Reproduced using 0.23.11` 6565c06
• Ubuntu 18.04 x64 - Reproduced using 0.23.11` 6565c06

[petemill]

@kjozwiak I discovered the issue you found is a regression due to some other changes, and would have happened without the animation this issue calls for, so created a new issue and will close this re-open in favor of #14477

[srirambv]

Verified on Windows 10 x64 using

• 0.23.16 - 2042c45
• Muon - 7.1.1
• libchromiumcontent - 67.0.3396.87

Verified with macOS 10.12.6 using

• 0.23.16 2042c45
• Muon 7.1.1
• libchromiumcontent 67.0.3396.87

Verified on Ubuntu 17.10 x64

• 0.23.17 - bc754eb
• Muon - 7.1.2
• libchromiumcontent - 67.0.3396.87