Twenty Thirteen: Button block not inheriting editor colors

[melchoyce]

The button block is not working correctly in Twenty Thirteen. I've noticed two issues:

• Filled buttons always inherit the shadow style, so the button always has a drop shadow. This happens both in the editor and on the front-end. This also happens on circular buttons. Because there is a specific button style for a filled button with a box shadow, this feels unepxected.
• Outlined buttons don't inherit any colors from the editor.

Attaching screenshots to show what I mean.

[melchoyce]

Buttons in the editor

[melchoyce]

Buttons on the front-end

Trac ticket: https://core.trac.wordpress.org/ticket/51223

---

This PR corrects the default color of outlined buttons in the editor. Originally, these were dark gray in the editor, and orange in the front end. Now they're orange in both places.

It also adds a new optional "No Shadow" block style which allows users to hide the 3px shadow on buttons if they'd like to. This seemed like a way to sort out the issue as noted in the ticket, while not changing the appearance of buttons on existing sites running this theme.

## Screenshots

Before:

After:

[melchoyce]

The PR works for me 👍

This does fix the color issue on default outline buttons, but I noticed a few other issues while testing:

• In firefox, I'm seeing dark borders on the buttons (seeing this on trunk too)
• On the outline button, background colors don't show up on the frontend
• When using a custom color for an outline button, the button disappears on hover/focus

Editor:
<img width="609" alt="Screen Shot 2021-02-15 at 11 39 52 AM" src="​https://user-images.githubusercontent.com/541093/107972943-94ee2a00-6f82-11eb-8ae9-47cf8b1c1d03.png">

Frontend:
<img width="585" alt="Screen Shot 2021-02-15 at 11 39 42 AM" src="​https://user-images.githubusercontent.com/541093/107972942-94559380-6f82-11eb-852a-541d6eabd4a1.png">

I'm not sure if you want to go down the rabbit hole of getting custom colors working - I think it would be enough of an improvement to fix the borders & make the outline button color consistent.

Yeah, that's definitely going to be a rabbit hole. I suggest we tackle those issues separately.

LGTM, just one comment about i18n...

@kjellr Did you also fix the border issue in Firefox? (in the screenshots above, the buttons all have dark borders)

@ryelle I can't reproduce those borders anymore — I wonder if they were fixed elsewhere?

I did add a couple extra commits that I think fix these two issues though:

• On the outline button, background colors don't show up on the frontend
• When using a custom color for an outline button, the button disappears on hover/focus

I think maybe it was fixed when ​https://github.com/WordPress/gutenberg/issues/29149 was fixed, I'm also not seeing the issue anymore. Everything looks good 👍

[ryelle]

The PR still looks good, let's get this fix in for 5.8.

[ryelle]

In 51110:

Twenty Thirteen: Add "No Shadow" style to button block.

This creates a new block style without a shadow, and fixes colors on outline buttons.

Props melchoyce, kjellr, scruffian.
Fixes #51223.

I'm not sure if this one is still valid. I'm unable to maintain it, would someone else mind adopting the PR?