Merging upstream version 127.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

2 files changed, 11 insertions, 11 deletions

diff --git a/browser/components/storybook/docs/README.other-widgets.stories.md b/browser/components/storybook/docs/README.other-widgets.stories.md
index b2614d88b6..3c6f8d63f2 100644
--- a/browser/components/storybook/docs/README.other-widgets.stories.md
+++ b/browser/components/storybook/docs/README.other-widgets.stories.md
@@ -30,8 +30,8 @@ Please refer to the existing [UA widgets documentation](https://firefox-source-d
 
 ### How to use existing Mozilla Custom Elements
 
-The existing Mozilla Custom Elements are automatically imported into all chrome privileged documents.
-These existing elements do not need to be imported individually via `<script>` tag or by using `window.ensureCustomElements()` when in a privileged main process document.
+The existing Mozilla Custom Elements are either [automatically imported](https://searchfox.org/mozilla-central/rev/d23849dd6d83edbe681d3b4828700256ea34a654/toolkit/content/customElements.js#853-878) into all chrome privileged documents, or are [lazy loaded](https://searchfox.org/mozilla-central/rev/d23849dd6d83edbe681d3b4828700256ea34a654/toolkit/content/customElements.js#789-809) and get automatically imported when first used.
+In either case, these existing elements do not need to be imported individually via `<script>` tag.
 As long as you are working in a chrome privileged document, you will have access to the existing Mozilla Custom Elements.
 You can dynamically create one of the existing custom elements by using `document.createDocument("customElement)` or `document.createXULElement("customElement")` in the relevant JS file, or by using the custom element tag in the relevant XHTML document.
 For example, `document.createXULElement("checkbox")` creates an instance of [widgets/checkbox.js](https://searchfox.org/mozilla-central/source/toolkit/content/widgets/checkbox.js) while using `<checkbox>` declares an instance in the XUL document.
@@ -74,11 +74,10 @@ Just like with the UI widgets, [the `browser_all_files_referenced.js` will fail
 
 ### Using new domain-specific widgets
 
-This is effectively the same as [using new design system components](#using-new-design-system-components).
-You will need to import your widget into the relevant `html`/`xhtml` files via a `script` tag with `type="module"`:
+This is effectively the same as [using new design system components](#using-new-design-system-components). In general you should be able to rely on these elements getting lazily loaded at the time of first use, similar to how existing custom elements are imported.
+
+Outside of chrome privileged documents you may need to import your widget into the relevant `html`/`xhtml` files via a `script` tag with `type="module"`:
 
 ```html
 <script type="module" src="chrome://browser/content/<domain-directory>/<your-widget>.mjs"></script>
 ```
-
-Or use `window.ensureCustomElements("<your-widget>")` as previously stated in [the using new design system components section.](#using-new-design-system-components)
diff --git a/browser/components/storybook/docs/README.reusable-widgets.stories.md b/browser/components/storybook/docs/README.reusable-widgets.stories.md
index f26c18a2b0..003cbc36bf 100644
--- a/browser/components/storybook/docs/README.reusable-widgets.stories.md
+++ b/browser/components/storybook/docs/README.reusable-widgets.stories.md
@@ -16,6 +16,8 @@ re-rendering logic. All new components are being documented in Storybook in an
 effort to create a catalog that engineers and designers can use to see which
 components can be easily lifted off the shelf for use throughout Firefox.
 
+If you want to see the progress over time of these new reusable components, we have a [Reusable Component Adoption chart](https://firefoxux.github.io/recomp-metrics/) that you should check out!
+
 ## Designing new reusable widgets
 
 Widgets that live at the global level, "UI Widgets", should be created in collaboration with the Design System team.
@@ -111,17 +113,16 @@ by updating [this array](https://searchfox.org/mozilla-central/rev/5c922d8b93b43
 
 Once you've added a new component to `toolkit/content/widgets` and created
 `chrome://` URLs via `toolkit/content/jar.mn` you should be able to start using it
-throughout Firefox. You can import the component into `html`/`xhtml` files via a
+throughout Firefox. In most cases, you should be able to rely on your custom element getting lazy loaded at the time of first use, provided you are working in a privileged context where `customElements.js` is available.
+
+You can import the component directly into `html`/`xhtml` files via a
 `script` tag with `type="module"`:
 
 ```html
 <script type="module" src="chrome://global/content/elements/your-component-name.mjs"></script>
 ```
 
-If you are unable to import the new component in html, you can use [`ensureCustomElements()` in customElements.js](https://searchfox.org/mozilla-central/rev/31f5847a4494b3646edabbdd7ea39cb88509afe2/toolkit/content/customElements.js#865) in the relevant JS file.
-For example, [we use `window.ensureCustomElements("moz-button-group")` in `browser-siteProtections.js`](https://searchfox.org/mozilla-central/rev/31f5847a4494b3646edabbdd7ea39cb88509afe2/browser/base/content/browser-siteProtections.js#1749).
-**Note** you will need to add your new widget to [the switch in importCustomElementFromESModule](https://searchfox.org/mozilla-central/rev/85b4f7363292b272eb9b606e00de2c37a6be73f0/toolkit/content/customElements.js#845-859) for `ensureCustomElements()` to work as expected.
-Once [Bug 1803810](https://bugzilla.mozilla.org/show_bug.cgi?id=1803810) lands, this process will be simplified: you won't need to use `ensureCustomElements()` and you will [add your widget to the appropriate array in customElements.js instead of the switch statement](https://searchfox.org/mozilla-central/rev/85b4f7363292b272eb9b606e00de2c37a6be73f0/toolkit/content/customElements.js#818-841).
+**Note** you will need to add your new widget to [this array in customElements.js](https://searchfox.org/mozilla-central/rev/cde3d4a8d228491e8b7f1bd94c63bbe039850696/toolkit/content/customElements.js#791-810) to ensure it gets lazy loaded on creation.
 
 ## Common pitfalls