Auto merge of #20689 - fabricedesre:mutation-take-records, r=emilio

MutationObserver api: Implement takeRecords() and characterData mutations

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I started by looking at adding support for `takeRecords()` to get fluent.js to work on Servo. To get the wpt tests to pass I ended up implementing character data mutations (most of the plumbing was already there) and this fixed a few more tests.

We are still missing support for `disconnect()`, which I keep for a followup.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach build-geckolib` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (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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tests/wpt/metadata/dom/nodes/MutationObserver-attributes.html.ini

@@ -1,28 +1,5 @@
 [MutationObserver-attributes.html]
   type: testharness
-  [attributes Element.id: same value mutation]
-    expected: FAIL
-
-  [attributes Element.className: new value mutation]
-    expected: FAIL
-
-  [attributes Element.classList.add: single token addition mutation]
-    expected: FAIL
-
-  [attributes Element.classList.add: multiple tokens addition mutation]
-    expected: FAIL
-
-  [attributes Element.setAttribute: classname mutation]
-    expected: FAIL
-
-  [attributes Element.setAttributeNS: creation mutation]
-    expected: FAIL
-
-  [attributes Element.setAttributeNS: prefixed attribute creation mutation]
-    expected: FAIL
-
-  [attributes Element.className: empty string update mutation]
-    expected: FAIL
 
   [attributes/attributeFilter Element.id/Element.className: update mutation]
     expected: FAIL
@@ -32,4 +9,3 @@
 
   [attributeFilter alone Element.id/Element.className: multiple filter update mutation]
     expected: FAIL
-

tests/wpt/metadata/dom/nodes/MutationObserver-characterData.html.ini

@@ -1,11 +1,6 @@
 [MutationObserver-characterData.html]
   type: testharness
   expected: TIMEOUT
-  [characterData Text.data: simple mutation without oldValue]
-    expected: TIMEOUT
-
-  [characterData Text.data: simple mutation]
-    expected: TIMEOUT
 
   [characterData Text.appendData: simple mutation]
     expected: TIMEOUT
@@ -15,46 +10,3 @@
 
   [characterData Text.appendData: null string mutation]
     expected: TIMEOUT
-
-  [characterData Text.insertData: simple mutation]
-    expected: TIMEOUT
-
-  [characterData Text.insertData: empty string mutation]
-    expected: TIMEOUT
-
-  [characterData Text.insertData: null string mutation]
-    expected: TIMEOUT
-
-  [characterData Text.deleteData: simple mutation]
-    expected: TIMEOUT
-
-  [characterData Text.deleteData: empty mutation]
-    expected: TIMEOUT
-
-  [characterData Text.replaceData: simple mutation]
-    expected: TIMEOUT
-
-  [characterData Text.replaceData: empty mutation]
-    expected: TIMEOUT
-
-  [characterData ProcessingInstruction: data mutations]
-    expected: TIMEOUT
-
-  [characterData Comment: data mutations]
-    expected: TIMEOUT
-
-  [characterData Range.deleteContents: child and data removal mutation]
-    expected: TIMEOUT
-
-  [characterData Range.deleteContents: child and data removal mutation (2)]
-    expected: TIMEOUT
-
-  [characterData Range.extractContents: child and data removal mutation]
-    expected: TIMEOUT
-
-  [characterData Range.extractContents: child and data removal mutation (2)]
-    expected: TIMEOUT
-
-  [characterData/characterDataOldValue alone Text.data: simple mutation]
-    expected: TIMEOUT
-

tests/wpt/metadata/dom/nodes/MutationObserver-takeRecords.html.ini

@@ -1,11 +1,2 @@
 [MutationObserver-takeRecords.html]
   type: testharness
-  [unreachabled test]
-    expected: FAIL
-
-  [All records present]
-    expected: FAIL
-
-  [No more records present]
-    expected: FAIL
-