Auto merge of #23777 - jdm:webgl-main-thread, r=asajeffrey

Support running WebGL in its own thread or on the main thread.

This is the final missing piece to support WebGL in ANGLE on Windows. ANGLE doesn't support multiple GL contexts on separate threads using the same underlying Direct3d device, so we need to process all GL operations for WebGL on the same thread as the compositor. These changes try to retain enough flexibility to support both approaches so we can get WebGL working on Windows ASAP.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23697
- [x] There are tests for these changes

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components/script/dom/bindings/trace.rs

@@ -54,6 +54,7 @@ use canvas_traits::webgl::{WebGLShaderId, WebGLTextureId, WebGLVersion, WebGLVer
 use crossbeam_channel::{Receiver, Sender};
 use cssparser::RGBA;
 use devtools_traits::{CSSError, TimelineMarkerType, WorkerId};
+use embedder_traits::EventLoopWaker;
 use encoding_rs::{Decoder, Encoding};
 use euclid::default::{Point2D, Rect, Rotation3D, Transform2D, Transform3D};
 use euclid::Length as EuclidLength;
@@ -146,7 +147,7 @@ pub unsafe trait JSTraceable {
     unsafe fn trace(&self, trc: *mut JSTracer);
 }
 
-unsafe_no_jsmanaged_fields!(Box<dyn TaskBox>);
+unsafe_no_jsmanaged_fields!(Box<dyn TaskBox>, Box<dyn EventLoopWaker>);
 
 unsafe_no_jsmanaged_fields!(CSSError);