Auto merge of #12794 - anholt:webgl-depthrange-validate, r=emilio

webgl: Validate that depthRange near <= far.

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Add a check for one of the subcases of webgl-specific.html.

I added a longer comment citing the spec than is common in the file -- we've found these kinds of citations really useful in Mesa, but if we want to keep it to the spec link, I could change it.

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- [ ] These changes fix #__ (github issue number if applicable).

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Fixes a subtest of webgl-specific.html.

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components/script/dom/webglrenderingcontext.rs

@@ -987,6 +987,15 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.3
     fn DepthRange(&self, near: f32, far: f32) {
+        // From the WebGL 1.0 spec, 6.12: Viewport Depth Range:
+        //
+        //     "A call to depthRange will generate an
+        //      INVALID_OPERATION error if zNear is greater than
+        //      zFar."
+        if near > far {
+            return self.webgl_error(InvalidOperation);
+        }
+
         self.ipc_renderer
             .send(CanvasMsg::WebGL(WebGLCommand::DepthRange(near as f64, far as f64)))
             .unwrap()