Auto merge of #13747 - scotttrinh:canvas-webidl, r=Ms2ger

Partial fix for #12415: expose Canvas interfaces

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Fix interface exposure per [the specs](https://html.spec.whatwg.org/multipage/scripting.html#2dcontext).

One lingering question I have is if [`CanvasPath`](https://html.spec.whatwg.org/multipage/scripting.html#canvaspath) needs to be added to `interfaces.worker.js` since it *is* exposed to the `Worker` environment. I tried adding it to the `interfaces.worker.js` list but it failed tests at https://github.com/servo/servo/blob/master/tests/wpt/mozilla/tests/mozilla/interfaces.js#L82

---
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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 contain a partial fix for #12415 (github issue number if applicable).

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

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tests/wpt/metadata/workers/semantics/interface-objects/002.worker.js.ini

@@ -9,21 +9,9 @@
   [The DOMImplementation interface object should not be exposed.]
     expected: FAIL
 
-  [The HTMLCanvasElement interface object should not be exposed.]
-    expected: FAIL
-
   [The MouseEvent interface object should not be exposed.]
     expected: FAIL
 
-  [The CanvasRenderingContext2D interface object should not be exposed.]
-    expected: FAIL
-
-  [The CanvasGradient interface object should not be exposed.]
-    expected: FAIL
-
-  [The CanvasPattern interface object should not be exposed.]
-    expected: FAIL
-
   [The PopStateEvent interface object should not be exposed.]
     expected: FAIL
 

tests/wpt/mozilla/tests/mozilla/interfaces.worker.js

@@ -10,9 +10,6 @@ test_interfaces([
   "Attr",
   "BeforeUnloadEvent",
   "Blob",
-  "CanvasGradient",
-  "CanvasRenderingContext2D",
-  "CanvasPattern",
   "CharacterData",
   "CloseEvent",
   "CSS",
@@ -45,7 +42,6 @@ test_interfaces([
   "HashChangeEvent",
   "Headers",
   "History",
-  "HTMLCanvasElement",
   "HTMLCollection",
   "HTMLElement",
   "HTMLFormControlsCollection",