Lower minimum window width to 375px

[philipp-spiess]

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Tested on (check one or more):

• Windows
• macOS
• Linux

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This PR changes the minimum window width such that the browser can size beyond 500px to make it easier to test responsive viewports without being forced to open devtools et al.

All of the research of this and the code was written by Codex but it seems trivial enough. I've been testing it on macOS.

To give some added context, the BrowserViewLayout::GetMinimumSize method is responsible for computing the minimum viewport and it does that by taking multiple minimums into accounts. In addition to changing two hardcoded minimum widths, the toolbar was constrained by the omnibox minimum characters.

However, reducing the omnibox min chars clashes with this change in the experimental one-line toolbar. To resolve this I'm proposing we hide the back, forward, and refresh buttons in these ultra-small viewports (<500px) and keep the min chars as-is.

Before

After

CleanShot.2025-12-21.at.23.05.24.mp4

[philipp-spiess]

Just noticed that this clashes with this change here: e9de843#diff-2826944ab8480d94ea497b4162f31b7ef9781cdfc282596674f87906931560c1R244-R245

One thing we could do to preserve some space in this view is to hide the back/forward/refresh buttons in small viewports? I had this working initially but decided to remove the code to keep the diff leaner.

[philipp-spiess]

Alright opening this up for review again. This PR now hides the back/forward/refresh buttons as suggested. PR description is updated and I made sure the code change is minimal. Attached is also a video of the new behavior in both modes. Would love some input at that point if know if you think this idea is worth exploring more :)