Auto merge of #17609 - asajeffrey:canvas-clear-state, r=jdm

Clear canvas thread state on recreation.

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The canvas rendering context is cleared when it is recreated, but not the matching state in the canvas paint thread.

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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 #17533
- [X] These changes do not require tests because the css-paint-api tests test for this already.

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tests/wpt/mozilla/meta/mozilla/css-paint-api/paint2d-composite.html.ini

@@ -1,4 +0,0 @@
-[paint2d-composite.html]
-  type: reftest
-  expected: FAIL
-  bug: https://github.com/servo/servo/issues/17533

tests/wpt/mozilla/meta/mozilla/css-paint-api/paint2d-shadows.html.ini

@@ -1,4 +0,0 @@
-[paint2d-shadows.html]
-  type: reftest
-  expected: FAIL
-  bug: https://github.com/servo/servo/issues/17533