Auto merge of #20317 - gootorov:webgl-getFramebufferAttachmentParameter, r=jdm

Implement WebGL getFrameBufferAttachmentParameter API

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Implementation of `getFramebufferAttachmentParameter` as in WebGL1 specification.

Part of https://github.com/servo/servo/issues/10209.

r? emilio or jdm.

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- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [x] There are tests for these changes

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components/canvas_traits/webgl.rs

@@ -219,6 +219,7 @@ pub enum WebGLCommand {
     GetVertexAttribOffset(u32, u32, WebGLSender<isize>),
     GetShaderInfoLog(WebGLShaderId, WebGLSender<String>),
     GetProgramInfoLog(WebGLProgramId, WebGLSender<String>),
+    GetFramebufferAttachmentParameter(u32, u32, u32, WebGLSender<i32>),
     PolygonOffset(f32, f32),
     RenderbufferStorage(u32, u32, i32, i32),
     ReadPixels(i32, i32, i32, i32, u32, u32, WebGLSender<Vec<u8>>),
@@ -490,6 +491,7 @@ impl fmt::Debug for WebGLCommand {
             GetProgramInfoLog(..) => "GetProgramInfoLog",
             GetVertexAttrib(..) => "GetVertexAttrib",
             GetVertexAttribOffset(..) => "GetVertexAttribOffset",
+            GetFramebufferAttachmentParameter(..) => "GetFramebufferAttachmentParameter",
             PolygonOffset(..) => "PolygonOffset",
             ReadPixels(..) => "ReadPixels",
             RenderbufferStorage(..) => "RenderbufferStorage",