Remove redundant RefCell from CanvasState struct

[chansuke]

Removed DomRefCell member wrappers from CanvasState.

---

• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes fix #23436 (GitHub issue number if applicable)

• There are tests for these changes OR
• These changes do not require tests because it only fixed redundancy.

---

This change is 

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/script/dom/canvasrenderingcontext2d.rs, components/script/dom/offscreencanvasrenderingcontext2d.rs
• @KiChjang: components/script/dom/canvasrenderingcontext2d.rs, components/script/dom/offscreencanvasrenderingcontext2d.rs

[highfive]

Warning

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

[CYBAI]

@bors-servo try=wpt

[bors-servo]

⌛ Trying commit 4271f26 with merge d055df5...

[paulrouget]

@bors-servo r+

[bors-servo]

📌 Commit 4271f26 has been approved by paulrouget

[bors-servo]

⚡ Previous build results for status-taskcluster are reusable. Rebuilding only linux-rel-css, linux-rel-wpt...

[bors-servo]

💔 Test failed - linux-rel-css

[CYBAI]

Failures in `linux-rel-css`

{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/2dcontext/fill-and-stroke-styles/2d.pattern.repeat.case.html", 
    "line": 38867, 
    "action": "test_result", 
    "expected": "OK"
}
{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/2dcontext/fill-and-stroke-styles/2d.pattern.repeat.unrecognised.html", 
    "line": 39584, 
    "action": "test_result", 
    "expected": "OK"
}
{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/2dcontext/fill-and-stroke-styles/2d.pattern.repeat.nullsuffix.html", 
    "line": 40139, 
    "action": "test_result", 
    "expected": "OK"
}
{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/2dcontext/fill-and-stroke-styles/2d.pattern.repeat.null.html", 
    "line": 40622, 
    "action": "test_result", 
    "expected": "OK"
}
{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/html/semantics/embedded-content/the-canvas-element/initial.reset.pattern.html", 
    "line": 106360, 
    "action": "test_result", 
    "expected": "OK"
}
{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/2dcontext/fill-and-stroke-styles/2d.fillStyle.parse.current.changed.html", 
    "line": 151463, 
    "action": "test_result", 
    "expected": "OK"
}
{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/2dcontext/fill-and-stroke-styles/2d.pattern.repeat.unrecognisednull.html", 
    "line": 152146, 
    "action": "test_result", 
    "expected": "OK"
}
{
    "status": "CRASH", 
    "group": "default", 
    "message": null, 
    "stack": null, 
    "subtest": null, 
    "test": "/2dcontext/fill-and-stroke-styles/2d.pattern.repeat.undefined.html", 
    "line": 173173, 
    "action": "test_result", 
    "expected": "OK"
}

[chansuke]

@CYBAI Thanks for your comment. How can I debug the error of linux-rel-css in my local env?

[CYBAI]

I think you can try to run these tests locally with ./mach test-wpt.

[jdm]

Specifically ./mach test-wpt /2dcontext/fill-and-stroke-styles/2d.pattern.repeat.case.html will run one failing test and show the output in the terminal.

[bors-servo]

☔ The latest upstream changes (presumably #23827) made this pull request unmergeable. Please resolve the merge conflicts.

[chansuke]

Sorry for taking time, the error says DomRefCell<T> already borrowed: so I at first tried to change this.canvas_state.borrow() ⇒ this.canvas_state.borrow() in canvasrenderingcontext2 and offscreencanvasrenderingcontext2d but could not get rid of the error, and am stacking right now.

[gterzian]

@chansuke since you transform some borrow into borrow_mut, and a borrow can be followed by another borrow but not a borrow_mut, it must be that somewhere where you introduced a borrow_mut, that which is borrowed mutably is already borrow immutably. Previously, the borrow was followed by another borrow, and now it's changed to a mutable borrow, hence the panic.

I can't tell why one it is though...

[jdm]

@bors-servo try=wpt
The previous logs disappeared.

[bors-servo]

⌛ Trying commit 266109c with merge d79010f...

[bors-servo]

💔 Test failed - linux-rel-css

[jdm]

The place to look will be:

 │    6: script::dom::htmlcanvaselement::HTMLCanvasElement::fetch_all_data::haa9dfca3363a0147 (0x55a11a8b1197)
  │    7: script::dom::canvasrenderingcontext2d::CanvasState::CreatePattern::h66931c48f7ad02c7 (0x55a11b28a860)
  │    8: <script::dom::canvasrenderingcontext2d::CanvasRenderingContext2D as script::dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasRenderingContext2DBinding::CanvasRenderingContext2DMethods>::CreatePattern::hf7505c94c50526e7 (0x55a11b290a03)

Presumably we borrow in CanvasRenderingContext2D::CreatePattern, then HTMLCanvasElement::fetch_all_data tries to borrow again when it's called from CanvasState::CreatePattern.

[bors-servo]

☔ The latest upstream changes (presumably #24340) made this pull request unmergeable. Please resolve the merge conflicts.

[jdm]

Closing due to inactivity.