Jetpack Tiled Gallery Block: save functionality

[illusaen]

Adding workaround to allow for loading of serialized HTML into the mobile editor. Currently using the workaround to unblock the rest of the block functionality that still needs to be done; will revisit in the future. One known bug is that loading a 1-column HTML still shows "Problem Displaying Block".

See issues:

• Jetpack Tiled Gallery: Workaround used for save functionality #4137
• Jetpack Tiled Gallery: Fix the save function when a single column is used #4142

Changes proposed in this Pull Request:

Allows us to load serialized HTML for the mobile app so that the saved Tiled Gallery Block shows up on the editor.

Does this pull request change what data or activity we track or use?

N/A

Testing instructions:

1. Create a tiled gallery block.
2. Add 2 images to the block.
3. Switch to HTML view.
4. Select all of the serialized HTML and cut.
5. Switch back to visual mode.
6. Switch to HTML mode again (these steps force the visual editor to update).
7. Paste in the HTML that was cut.
8. Switch back to visual mode.
9. See that the correct Tiled Gallery Block shows up.

Screenshots:

screen-20211020-153558.mp4

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ⚠️ All commits were linted before commit.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• 🔴 Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

---

🔴 Action required: Please add missing changelog entries for the following projects: projects/plugins/jetpack

Use the Jetpack CLI tool to generate changelog entries by running the following command: jetpack changelog add.
Guidelines: /docs/writing-a-good-changelog-entry.md

---

Once your PR is ready for review, check one last time that all required checks (other than "Required review") appearing at the bottom of this PR are passing or skipped.
Then, add the "[Status] Needs Team review" label and ask someone from your team review the code.
Once you’ve done so, switch to the "[Status] Needs Review" label; someone from Jetpack Crew will then review this PR and merge it to be included in the next Jetpack release.

---

Jetpack plugin:

• Next scheduled release: November 2, 2021.
• Scheduled code freeze: October 25, 2021.

[guarani]

I tested this and it's working well. I didn't see any issues after three attempts.
If we find any issues with this workaround we can of course fix them in a separate PR.
Thanks for finding this solution @illusaen!

[guarani]

From the "Could not cleanly apply this PR to synced wpcom files" message under CI checks, it looks like there was an issue syncing to WP.com. I've ran into a similar error and was told it's safe to ignore (and is likely due to unrelated issue). If syncing had worked, we were going to mark the sync "abandoned" since we're not merging to master yet, so this seems safe to ignore.

[jeherve]

we're not merging to master yet, so this seems dafe to ignore.

Exactly. Since you're merging into a feature branch, this can be ignored for now.