Implement GPUBuffer.mapAsync and update wgpu-core

[kunalmohan]

This PR covers the following-

1. update wgpu-core to use serializable RenderPass and ComputePass. Implement DispatchIndirect.
2. Implement GPUBuffer.mapAsync().

The mapAsync() methods has the following flow-

1. A new promise is created in mapAsync() and a message sent to the server-side. This returns a promise.
2. On the server-side, a struct BufferMapInfo object stores the relevant info required to send data to the client-side on completion of mapping. This object is stored in a buffer_maps: HashMap<id::BufferId, BufferMapInfo<'a>>, in WGPU. buffers_maps basically stores the data for buffers with pending mapping.
3. buffer_map_async() command is issued with a callback responsible to send the data back to the client.
4. All the devices are polled every time the server receives a new message.
5. The data is sent back on completion and promise resolved through AsyncWGPUListener (similar to how the requestDevice() and RequestAdapter are processed).
6. On receiving the data, the client sends back a BufferMapComplete message to the server to remove the entry from buffer_maps hashmap.

I intended to implement getMappedRange(), too, in this PR but it's quite a task in itself (implementing intersecting ArrayBuffers). This already being a 500+ line PR, I thought it best to get this model approved first (also it will probably be easier to review this and getMappedRange separately). getMappedRange would come up in the next one.

---

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

• There are tests for these changes OR
• These changes do not require tests because ___

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/script/dom/webidls/GPUComputePassEncoder.webidl, components/script/dom/gpucomputepassencoder.rs, components/script/dom/gpumapmode.rs, components/script/dom/gpubuffer.rs, components/script/dom/webidls/GPUBuffer.webidl and 10 more
• @KiChjang: components/script/dom/webidls/GPUComputePassEncoder.webidl, components/script/dom/gpucomputepassencoder.rs, components/script/dom/gpumapmode.rs, components/script/dom/gpubuffer.rs, components/script/dom/webidls/GPUBuffer.webidl and 10 more

[highfive]

Warning

• These commits modify unsafe code. Please review it carefully!
• These commits modify script code, but no tests are modified. Please consider adding a test!

[kunalmohan]

r?@kvark

[kvark]

All the devices are polled every time the server receives a new message.

That's technically fine, but a bit scary nonetheless. In Gecko, we are polling the devices every 100ms, which is supposed to be configurable in the future, see code. Might be worth doing something like this in Servo.

[kvark]

Very nice! Just a few notes here

[kunalmohan]

I have addressed most of the review comments. I am still unsure about the last one- about how that would be done. I'll try to dig into it but maybe it will be better to solve that along with get_mapped_range() depending how the data will be exposed to the user. I can convert this to a draft and continue implementing get_mapped_range() here itself if that's a better idea.

(This line count of PR increased just because of new TAB space for the full block of code inside run() in webgpu/lib.rs)

[kvark]

We had a chat about this on "#wgpu:matrix.org", and it looks like the PR is on the right track:)

[kunalmohan]

@kvark I have changed the Unmapping process to use get_mapped_range() to write back the data to buffer while unmapping in case of mapAsync as well as mapped_at_creation.

[kvark]

Looks reasonable, thank you!

[kvark]

@bors-servo r+

[bors-servo]

📌 Commit 183a43d has been approved by kvark

[kunalmohan]

error[E0599]: no method named `handle_mut` found for struct `dom::bindings::trace::RootedTraceableBox<mozjs_sys::jsgc::Heap<*mut js::jsapi::JSObject>>` in the current scope
    --> components/script/dom/gpubuffer.rs:284:62
     |
284  |                         MutableHandle::from_raw(self.mapping.handle_mut()),
     |                                                              ^^^^^^^^^^ method not found in `dom::bindings::trace::RootedTraceableBox<mozjs_sys::jsgc::Heap<*mut js::jsapi::JSObject>>`
     | 
    ::: components/script/dom/bindings/trace.rs:1036:1
     |
1036 | pub struct RootedTraceableBox<T: 'static + JSTraceable> {
     | ------------------------------------------------------- method `handle_mut` not found for this
error[E0599]: no method named `handle_mut` found for struct `dom::bindings::trace::RootedTraceableBox<mozjs_sys::jsgc::Heap<_>>` in the current scope
    --> components/script/dom/gpudevice.rs:189:53
     |
189  |                     MutableHandle::from_raw(mapping.handle_mut()),
     |                                                     ^^^^^^^^^^ method not found in `dom::bindings::trace::RootedTraceableBox<mozjs_sys::jsgc::Heap<_>>`
     | 
    ::: components/script/dom/bindings/trace.rs:1036:1
     |
1036 | pub struct RootedTraceableBox<T: 'static + JSTraceable> {
     | ------------------------------------------------------- method `handle_mut` not found for this

checks failed. I didn't get this on my system earlier, but on a rebase against master I can see it failing now. I'll rectify this and push the changes.

[kvark]

@bors-servo r+

[bors-servo]

📌 Commit db2d313 has been approved by kvark

[bors-servo]

⌛ Testing commit db2d313 with merge 1ea332e...

[bors-servo]

💔 Test failed - status-taskcluster

[jdm]

@bors-servo retry

• #25522

[bors-servo]

⌛ Testing commit db2d313 with merge af110ac...

[bors-servo]

☀️ Test successful - status-taskcluster
Approved by: kvark
Pushing af110ac to master...