Add GPUSampler to WebGPU implementation

Add dom_struct and webidl for GPUSampler, implement GPUDevice.createSampler() method.

components/script/dom/gpusampler.rs

@@ -0,0 +1,77 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::codegen::Bindings::GPUSamplerBinding::GPUSamplerMethods;
+use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
+use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::str::DOMString;
+use crate::dom::globalscope::GlobalScope;
+use dom_struct::dom_struct;
+use std::cell::Cell;
+use webgpu::{WebGPU, WebGPUDevice, WebGPUSampler};
+
+#[dom_struct]
+pub struct GPUSampler {
+    reflector_: Reflector,
+    #[ignore_malloc_size_of = "channels are hard"]
+    channel: WebGPU,
+    label: DomRefCell<Option<DOMString>>,
+    device: WebGPUDevice,
+    compare_enable: bool,
+    sampler: WebGPUSampler,
+    valid: Cell<bool>,
+}
+
+impl GPUSampler {
+    fn new_inherited(
+        channel: WebGPU,
+        device: WebGPUDevice,
+        compare_enable: bool,
+        sampler: WebGPUSampler,
+        valid: bool,
+    ) -> GPUSampler {
+        Self {
+            reflector_: Reflector::new(),
+            channel,
+            label: DomRefCell::new(None),
+            valid: Cell::new(valid),
+            device,
+            sampler,
+            compare_enable,
+        }
+    }
+
+    pub fn new(
+        global: &GlobalScope,
+        channel: WebGPU,
+        device: WebGPUDevice,
+        compare_enable: bool,
+        sampler: WebGPUSampler,
+        valid: bool,
+    ) -> DomRoot<GPUSampler> {
+        reflect_dom_object(
+            Box::new(GPUSampler::new_inherited(
+                channel,
+                device,
+                compare_enable,
+                sampler,
+                valid,
+            )),
+            global,
+        )
+    }
+}
+
+impl GPUSamplerMethods for GPUSampler {
+    /// https://gpuweb.github.io/gpuweb/#dom-gpuobjectbase-label
+    fn GetLabel(&self) -> Option<DOMString> {
+        self.label.borrow().clone()
+    }
+
+    /// https://gpuweb.github.io/gpuweb/#dom-gpuobjectbase-label
+    fn SetLabel(&self, value: Option<DOMString>) {
+        *self.label.borrow_mut() = value;
+    }
+}