Auto merge of #26423 - asajeffrey:webxr-glwindow-blit, r=Manishearth

Workarounds for webxr glwindow on macos

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Makes the default glwindow mode one which does blitting rather than using a shader, since that works on macos.

---
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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 #26340

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components/config/prefs.rs

@@ -300,6 +300,8 @@ mod gen {
                     glwindow: {
                         #[serde(default)]
                         enabled: bool,
+                        #[serde(rename = "dom.webxr.glwindow.left-right")]
+                        left_right: bool,
                         #[serde(rename = "dom.webxr.glwindow.red-cyan")]
                         red_cyan: bool,
                     },