Auto merge of #27154 - kunalmohan:async-presentation, r=kvark

WebGPU update presentation data asynchronously

<!-- Please describe your changes on the following line: -->
This PR aims to make updating Webrender presentation data non-blocking.
A callback is passed to the `buffer_map_async()` fn wherein the data is read and a message sent to the server itself to write the data into the shared `PresentationData` struct object.

r?@kvark

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___

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components/script/dom/gpubuffer.rs

@@ -16,6 +16,7 @@ use crate::dom::promise::Promise;
 use crate::realms::InRealm;
 use crate::script_runtime::JSContext;
 use dom_struct::dom_struct;
+use ipc_channel::ipc::IpcSharedMemory;
 use js::jsapi::DetachArrayBuffer;
 use js::jsapi::NewExternalArrayBuffer;
 use js::jsapi::{Heap, JSObject};
@@ -150,7 +151,7 @@ impl GPUBufferMethods for GPUBuffer {
                 let m_range = m_info.mapping_range.clone();
                 if let Err(e) = self.channel.0.send(WebGPURequest::UnmapBuffer {
                     buffer_id: self.id().0,
-                    array_buffer: m_info.mapping.borrow().clone(),
+                    array_buffer: IpcSharedMemory::from_bytes(m_info.mapping.borrow().as_slice()),
                     is_map_read: m_info.map_mode == Some(GPUMapModeConstants::READ),
                     offset: m_range.start,
                     size: m_range.end - m_range.start,
@@ -325,7 +326,7 @@ impl AsyncWGPUListener for GPUBuffer {
                     .as_mut()
                     .unwrap()
                     .mapping
-                    .borrow_mut() = bytes;
+                    .borrow_mut() = bytes.to_vec();
                 promise.resolve_native(&());
                 self.state.set(GPUBufferState::Mapped);
             },

components/script/dom/gpucanvascontext.rs

@@ -18,12 +18,13 @@ use crate::dom::globalscope::GlobalScope;
 use crate::dom::gpuswapchain::GPUSwapChain;
 use crate::dom::htmlcanvaselement::{HTMLCanvasElement, LayoutCanvasRenderingContextHelpers};
 use crate::dom::node::{document_from_node, Node, NodeDamage};
+use arrayvec::ArrayVec;
 use dom_struct::dom_struct;
 use euclid::default::Size2D;
 use ipc_channel::ipc;
 use script_layout_interface::HTMLCanvasDataSource;
 use std::cell::Cell;
-use webgpu::{wgt, WebGPU, WebGPURequest};
+use webgpu::{wgpu::id, wgt, WebGPU, WebGPURequest};
 
 #[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Ord, PartialEq, PartialOrd)]
 pub struct WebGPUContextId(pub u64);
@@ -91,7 +92,6 @@ impl GPUCanvasContext {
             external_id: self.context_id.0,
             texture_id,
             encoder_id,
-            image_key: self.webrender_image.get().unwrap(),
         }) {
             warn!(
                 "Failed to send UpdateWebrenderData({:?}) ({})",
@@ -130,11 +130,15 @@ impl GPUCanvasContextMethods for GPUCanvasContext {
         }
         *self.swap_chain.borrow_mut() = None;
 
-        let buffer_id = self
-            .global()
-            .wgpu_id_hub()
-            .lock()
-            .create_buffer_id(descriptor.device.id().0.backend());
+        let mut buffer_ids = ArrayVec::<[id::BufferId; 5]>::new();
+        for _ in 0..5 {
+            buffer_ids.push(
+                self.global()
+                    .wgpu_id_hub()
+                    .lock()
+                    .create_buffer_id(descriptor.device.id().0.backend()),
+            );
+        }
 
         let image_desc = webrender_api::ImageDescriptor {
             format: match descriptor.format {
@@ -166,7 +170,7 @@ impl GPUCanvasContextMethods for GPUCanvasContext {
             .0
             .send(WebGPURequest::CreateSwapChain {
                 device_id: descriptor.device.id().0,
-                buffer_id,
+                buffer_ids,
                 external_id: self.context_id.0,
                 sender,
                 image_desc,