Auto merge of #24564 - paulrouget:initButtons, r=jdm

Properly set MouseEvent buttons property

Properly set MouseEvent buttons property. Same behavior as Chrome and Firefox.

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #24363 (GitHub issue number if applicable)

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because ___

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components/script/dom/mouseevent.rs

@@ -137,7 +137,7 @@ impl MouseEvent {
             init.parent.shiftKey,
             init.parent.metaKey,
             init.button,
-            0,
+            init.buttons,
             init.relatedTarget.as_deref(),
             None,
         );

tests/wpt/metadata/dom/events/Event-subclasses-constructors.html.ini

@@ -1,8 +1,5 @@
 [Event-subclasses-constructors.html]
   type: testharness
-  [MouseEvent constructor (argument with non-default values)]
-    expected: FAIL
-
   [WheelEvent constructor (argument with non-default values)]
     expected: FAIL