Upgrade wgpu version to "0.5.0" and add server-side code for id recycling for WebGPU

[kunalmohan]

I have updated the cargo.lock to use a wgpu-core at a more recent commit where IdentityHandlerFactory was introduced.
r?@kvark

---

• ./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/identityhub.rs
• @KiChjang: components/script/dom/identityhub.rs, components/script_traits/script_msg.rs

[highfive]

Warning

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

[kunalmohan]

@kvark could you take a look at this before I proceed further?
Version update isn't complete yet. I'll open a separate PR first to update the existing implementation to the required commit version of wgpu-core and rebase this.

[kvark]

Thank you, this is one of the critical things we were missing!
Expressed some ideas on how we can rework this to be even better :)

[kunalmohan]

It was difficult to upgrade to 0.5 without implementing the IdentityRecyclerFactory, so I have completed the task here itself. This PR now covers the following-

1. Upgrade to version wgpu-core 0.5
2. Since the spec doesn't include MapReadAsync anymore, I have removed it completely (instead of updating it with the version).
3. Implement the server-side part for id recycling.

[kunalmohan]

The upgrade has introduced duplicate dependencies-

./Cargo.lock:1: duplicate versions for package `ron`
	The following packages depend on version 0.1.7 from 'crates.io':
	The following packages depend on version 0.5.1 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `parking_lot_core`
	The following packages depend on version 0.6.2 from 'crates.io':
	The following packages depend on version 0.7.2 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `metal`
	The following packages depend on version 0.17.0 from 'crates.io':
	The following packages depend on version 0.18.0 from 'crates.io':
./Cargo.lock:1: duplicate versions for package `parking_lot`
	The following packages depend on version 0.10.2 from 'crates.io':
	The following packages depend on version 0.9.0 from 'crates.io':

I tried resolving them with ./mach cargo-update .. but wasn't successful.

[kvark]

The upgrade has introduced duplicate dependencies

Then we need a separate PR to Servo that bumps parking_lot, another one that bumps RON.

[jdm]

You can add duplicates to servo-tidy.toml if it's not straightforward to update the packages that depend on the older versions.

[jdm]

And yes, the output from tidy in that case is less helpful than it could be: #25508

[kvark]

I think it looks good now. Have a few more minor suggestions.
The main unresolved thing is duplicated dependencies. If @jdm is fine to follow up with them, so be it:)

[kunalmohan]

@jdm parking_lot is a dependency of many packages, one of which is Surfman. metal also is a dependency for Surfman. ron is required by Webrender. I guess upgrading them wouldn't be possible from here. So I'll proceed with the servo-tidy.toml option. Or should I open PRs in respective repositories?

[jdm]

opening pull requests can't hurt!

[jdm]

but yes, no need to gate this PR on those other repositories.

[kunalmohan]

I have made the required changes and squashed the commits.

[jdm]

@bors-servo r=kvark

[bors-servo]

📌 Commit a4f9116 has been approved by kvark

[bors-servo]

⌛ Testing commit a4f9116 with merge 137803c...

[bors-servo]

💔 Test failed - status-taskcluster

[jdm]

thread 'rustc' panicked at 'could not find markdown in source', src/librustdoc/passes/mod.rs:411:31
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:78
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:59
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1069
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1504
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:62
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:49
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:218
  10: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:511
  11: rust_begin_unwind
             at src/libstd/panicking.rs:419
  12: core::panicking::panic_fmt
             at src/libcore/panicking.rs:111
  13: core::option::expect_failed
             at src/libcore/option.rs:1260
  14: rustdoc::passes::source_span_for_markdown_range
  15: <rustdoc::passes::check_code_block_syntax::SyntaxChecker as rustdoc::fold::DocFolder>::fold_item
  16: <alloc::vec::Vec<T> as alloc::vec::SpecExtend<T,I>>::from_iter
  17: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::fold
  18: <std::collections::hash::map::HashMap<K,V,S> as core::iter::traits::collect::FromIterator<(K, V)>>::from_iter
  19: rustdoc::passes::check_code_block_syntax::check_code_block_syntax
  20: rustc_middle::ty::context::tls::enter_global
  21: rustc_interface::interface::run_compiler_in_existing_thread_pool
  22: rustdoc::core::run_core
  23: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  24: rustc_driver::catch_fatal_errors
error: Could not document `gfx-backend-empty`.

[kvark]

This is rust-lang/rust#70874, which was fixed. Sounds like we need a rustc version update in Servo before moving on?

[jdm]

@kunalmohan You should be able to change the nightly version in the rust-toolchain file to any nightly that is older than 5/19/2020.

[kunalmohan]

I was getting this warning at a few places after toolchain update-
unused return value of `std::mem::replace` that must be used
So I have prefixed the statements with let _ =

[jdm]

@bors-servo r+

[bors-servo]

📌 Commit f3fa53b has been approved by jdm

[bors-servo]

⌛ Testing commit f3fa53b with merge 94063d6...

[bors-servo]

☀️ Test successful - status-taskcluster
Approved by: jdm
Pushing 94063d6 to master...