Initial Prototype of Find in HtmlPreviewPart

[hoovercj]

This is what I came up with to address #2187.

I based it on the FindWidget and in fact have imported some code from there, and for the moment have duplicated some of the CSS as well. Consider that a WIP to be cleaned up if this overall approach is accepted.

The main parts of the pull request are:

• SimpleFindState: Maintains the visible state of the widget and the state of the results. Notifies listeners when they change
• Webview: add hooks for finding in the page and emitting results
• FindModelBoundToWebView: As the name implies, this is the model that is bound to the webview implementation details. It updates the state when the webview returns results
• SimpleFindWidget: Has the input and buttons, receives state changes to update the text and buttons and asks the model to search when buttons are pressed
• HtmlPreviewPart: Composes everything.

Thoughts?

[mention-bot]

@hoovercj, thanks for your PR! By analyzing the history of the files in this pull request, we identified @alexandrudima and @jrieken to be potential reviewers.

[msftclas]

@hoovercj,
Thanks for your contribution as a Microsoft full-time employee or intern. You do not need to sign a CLA.
Thanks,
Microsoft Pull Request Bot

[hoovercj]

tagging @mjbvz as well

[mjbvz]

This looks pretty sweet. Nice work!

I can provide more feedback tomorrow.� Also, @jrieken and @alexandrudima know much more about existing find implementation and should be able to provide better feedback/advice.

The overall approach seems solid to me at least, with my main concern at present being the amount duplicated code and styling. It sounds like you are also aware of this issue and are working to address it. I could see FindWidget either becoming an abstract class that is specialized for the editor and for the webview, or, perhaps better, having the FindWidget some additional set of adapters/config-objects that specialize its behavior and appearance based on what is needed

[hoovercj]

Superceded by #30016