Resize handle for vertical tab strip

[sangwoo108]

Currently, vertical tab strip has fixed width. But it'd be useful if we can resize it with a resize handle.

[spotco]

Was google-ing how to do this in brave with brave://flags/#brave-vertical-tabs enabled.
Looking forward to seeing this in - thank you very much!

[stephendonner]

Verified PASSED using

Brave	1.53.67 Chromium: 114.0.5735.53 (Official Build) beta (x86_64)
Revision	c499d7ea22c8b2dba278465a5df7b86a8efa4e64-refs/branch-heads/5735@{#970}
OS	macOS Version 11.7.7 (Build 20G1345)

Steps:

1. installed 1.53.67
2. launched Brave
3. context-clicked my open tab
4. chose Use Vertical Tabs
5. played around with the dynamic tab-pane resizer

Confirmed:

• minimum and maximum viewport sizes (see attached screenshots)
• no crashes
• chosen tab-pane width persists between new windows
• tab titles get covered and uncovered without any glyphs

example	example

example	example

[kjozwiak]

Added QA/Test-All-Platforms due to platforms like Linux having a history of crashing when resizing/moving tabs around etc.. Would be useful to check all platforms just to make sure resizing isn't causing any obvious issues.

[MadhaviSeelam]

Verification PASSED

Brave | 1.53.76 Chromium: 114.0.5735.90 (Official Build) beta (64-bit)
-- | --
Revision | 386bc09e8f4f2e025eddae123f36f6263096ae49-refs/branch-heads/5735@{#1052}
OS | Windows 11 Version 22H2 (Build 22621.1702)

Steps:

1. installed 1.53.76
2. launched Brave
3. context-clicked my open tab
4. chose Use Vertical Tabs
5. played around with the dynamic tab-pane resizer
6. closed and restarted Brave

Confirmed:

• dragging the right side of vertical tab strip changed the width to minimum & maximum viewport sizes
• no crashes
• chosen tab-pane width persists between new windows
• tab titles get covered and uncovered without any glyphs
• double clicked on the resizer handle to return to default width
• changed width was persistent after restarting the browser.

2023-06-01_13h56_58.mp4

[MadhaviSeelam]

Verification PASSED using

Brave | 1.53.85 Chromium: 114.0.5735.110 (Official Build) beta (64-bit)
-- | --
Revision | 1c828682b85bbc70230a48f5e345489ec447373e-refs/branch-heads/5735_90@{#13}
OS | Linux

Steps:

1. installed 1.53.85
2. launched Brave
3. context-clicked my open tab
4. chose Use Vertical Tabs
5. played around with the dynamic tab-pane resizer
6. closed and restarted Brave

Confirmed:

• dragging the right side of vertical tab strip changed the width to minimum & maximum viewport sizes
• no crashes
• chosen tab-pane width persists between new windows
• tab titles get covered and uncovered without any glyphs
• double clicked on the resizer handle to return to default width
• changed width was persistent after restarting the browser.

2023-06-08_13h23_44.mp4

[Sa-Ja-Di]

Does not work here with the right now installable 1.53.83 Beta - can not resize tabs under Windows here - how to enable this feature?

[MadhaviSeelam]

@Sa-Ja-Di Can not resize in mouseover/minimized mode but able to resize in expanded mode. Here is the recording.

2023-06-08_16h59_08.mp4

[Sa-Ja-Di]

Correction.... after resetting some vertical tab flags i can resize them as it seems.

But i have discovered another issue related to vertical tabs now since a while in the way that when you open tons of fresh tabs and you close them, the side tab bar size seems not to be calculated correctly anymore and you can basically scroll away all the tabs you have left out of the screen - even if it is only 1 or 2 left which are open:
#30728