Bugzilla

By enabling the `<input type="search">` clear search button in privileged documents, regardless of the `layout.forms.input-type-search.enabled` pref, would be beneficial for the following reasons:
- It enables the moz-input-search component to be utilized in our UI without needing to create a duplicate implementation of the "clear search" functionality
- It allows us to consolidate and merge duplicate "search box with clear button" implementations:
  - [Firefox View](https://searchfox.org/mozilla-central/source/browser/components/firefoxview/fxview-search-textbox.mjs#115)
  - [DevTools](https://searchfox.org/mozilla-central/source/devtools/client/inspector/index.xhtml)
  - [GeckoView](https://searchfox.org/mozilla-central/source/mobile/shared/chrome/geckoview/config.xhtml#42)
- It increases visibility of the "clear search" button and any user experience issues with said input without impacting the entire web
- It moves us closer to being able to turn on `layout.forms.input-type-search.enabled` by default (Bug 1654288)

We will need to address the previous cases before enabling the "clear search" button, otherwise each of the cases will have duplicate buttons that are styled differently.

By enabling the `<input type="search">` clear search button in privileged documents, regardless of the `layout.forms.input-type-search.enabled` pref, would be beneficial for the following reasons:
- It enables the moz-input-search component to be utilized in our UI without needing to create a duplicate implementation of the "clear search" functionality
- It allows us to consolidate and merge duplicate "search box with clear button" implementations:
  - [Firefox View](https://searchfox.org/mozilla-central/source/browser/components/firefoxview/fxview-search-textbox.mjs#115)
    - Changing this one should also affect the sidebar, since the "Tabs from other devices" and "History" sections also use this particular search textbox.
  - [DevTools](https://searchfox.org/mozilla-central/source/devtools/client/inspector/index.xhtml)
  - [GeckoView](https://searchfox.org/mozilla-central/source/mobile/shared/chrome/geckoview/config.xhtml#42)
- It increases visibility of the "clear search" button and any user experience issues with said input without impacting the entire web
- It moves us closer to being able to turn on `layout.forms.input-type-search.enabled` by default (Bug 1654288)

We will need to address the previous cases before enabling the "clear search" button, otherwise each of the cases will have duplicate buttons that are styled differently.