canvas: Add vello_cpu backend (#38282)

vello_cpu does not have any tests timeouts, because we do not need
download stuff from GPU as all work happens on CPU. So performance wise
it's better then classic vello at least for our usecase. There are some
vello bugs, but I think we will be able to sort them out within
upstream, eventually. Interestingly enough there are no new PASS like
they were with classic vello.

Difference with raqote can be observed here:
https://github.com/sagudev/servo/actions/runs/16549241085/attempts/1#summary-46802486798

## Known vello problems:

- https://github.com/linebender/vello/issues/1119
- https://github.com/linebender/vello/issues/1056
-
`/html/canvas/element/fill-and-stroke-styles/2d.gradient.interpolate.coloralpha.html`
- `kurbo::Cap::Butt` is defect (only visible with big lineWidth)
https://github.com/linebender/vello/issues/1063
  - `/html/canvas/element/line-styles/2d.line.cross.html`
  - `/html/canvas/element/line-styles/2d.line.miter.acute.html`
- other lack of strong correct problems
(https://github.com/linebender/vello/issues/1063#issuecomment-2998084736):
  - `/html/canvas/element/path-objects/2d.path.rect.selfintersect.html`
- `putImageData(getImageData(...), ...)` is lossy (precision problems,
might be due to ImageData being unmultiplied)
-
`/html/canvas/element/pixel-manipulation/2d.imageData.put.unchanged.html`

Testing: Tested using vello_cpu_canvas subsuite

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

tests/wpt/meta/html/canvas/element/compositing/2d.composite.clip.clear.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.clip.clear.html]
+  [fill() does not affect pixels outside the clip region.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.clip.copy.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.clip.copy.html]
+  [fill() does not affect pixels outside the clip region.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.clip.destination-atop.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.clip.destination-atop.html]
+  [fill() does not affect pixels outside the clip region.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.clip.destination-in.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.clip.destination-in.html]
+  [fill() does not affect pixels outside the clip region.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.clip.source-in.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.clip.source-in.html]
+  [fill() does not affect pixels outside the clip region.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.clip.source-out.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.clip.source-out.html]
+  [fill() does not affect pixels outside the clip region.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.uncovered.pattern.copy.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.uncovered.pattern.copy.html]
+  [Pattern fill() draws pixels not covered by the source object as (0,0,0,0), and does not leave the pixels unchanged.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.uncovered.pattern.destination-atop.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.uncovered.pattern.destination-atop.html]
+  [Pattern fill() draws pixels not covered by the source object as (0,0,0,0), and does not leave the pixels unchanged.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.uncovered.pattern.destination-in.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.uncovered.pattern.destination-in.html]
+  [Pattern fill() draws pixels not covered by the source object as (0,0,0,0), and does not leave the pixels unchanged.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.uncovered.pattern.source-in.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.uncovered.pattern.source-in.html]
+  [Pattern fill() draws pixels not covered by the source object as (0,0,0,0), and does not leave the pixels unchanged.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/compositing/2d.composite.uncovered.pattern.source-out.html.ini

@@ -0,0 +1,4 @@
+[2d.composite.uncovered.pattern.source-out.html]
+  [Pattern fill() draws pixels not covered by the source object as (0,0,0,0), and does not leave the pixels unchanged.]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/drawing-rectangles-to-the-canvas/2d.clearRect.clip.html.ini

@@ -0,0 +1,4 @@
+[2d.clearRect.clip.html]
+  [clearRect is affected by clipping regions]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/drawing-rectangles-to-the-canvas/2d.clearRect.shadow.html.ini

@@ -0,0 +1,4 @@
+[2d.clearRect.shadow.html]
+  [clearRect does not draw shadows]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/drawing-rectangles-to-the-canvas/2d.clearRect.zero.html.ini

@@ -0,0 +1,4 @@
+[2d.clearRect.zero.html]
+  [clearRect of zero pixels has no effect]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/fill-and-stroke-styles/2d.gradient.interpolate.coloralpha.html.ini

@@ -3,3 +3,4 @@
     bug: https://github.com/linebender/vello/issues/1056
     expected:
       if subsuite == "vello_canvas": FAIL
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/fill-and-stroke-styles/2d.gradient.radial.cone.front.html.ini

@@ -0,0 +1,4 @@
+[2d.gradient.radial.cone.front.html]
+  [Canvas test: 2d.gradient.radial.cone.front]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/fill-and-stroke-styles/2d.gradient.radial.cone.top.html.ini

@@ -0,0 +1,4 @@
+[2d.gradient.radial.cone.top.html]
+  [Canvas test: 2d.gradient.radial.cone.top]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/fill-and-stroke-styles/2d.gradient.radial.inside2.html.ini

@@ -0,0 +1,4 @@
+[2d.gradient.radial.inside2.html]
+  [Canvas test: 2d.gradient.radial.inside2]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/fill-and-stroke-styles/2d.gradient.radial.inside3.html.ini

@@ -0,0 +1,4 @@
+[2d.gradient.radial.inside3.html]
+  [Canvas test: 2d.gradient.radial.inside3]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/fill-and-stroke-styles/2d.gradient.radial.outside1.html.ini

@@ -0,0 +1,4 @@
+[2d.gradient.radial.outside1.html]
+  [Canvas test: 2d.gradient.radial.outside1]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/fill-and-stroke-styles/2d.gradient.radial.outside3.html.ini

@@ -2,3 +2,4 @@
   [Canvas test: 2d.gradient.radial.outside3]
     expected:
       if subsuite == "": FAIL
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/line-styles/2d.line.cross.html.ini

@@ -3,3 +3,4 @@
     bug: https://github.com/linebender/vello/issues/1063
     expected:
       if subsuite == "vello_canvas": FAIL
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/path-objects/2d.path.arc.scale.1.html.ini

@@ -2,3 +2,4 @@
   [Non-uniformly scaled arcs are the right shape]
     expected:
       if subsuite == "vello_canvas": FAIL
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/path-objects/2d.path.rect.selfintersect.html.ini

@@ -1,5 +1,6 @@
 [2d.path.rect.selfintersect.html]
   [Canvas test: 2d.path.rect.selfintersect]
-    bug: https://github.com/linebender/vello/issues/1063#issuecomment-2998084736
+    bug: https://github.com/linebender/vello/issues/1063  #issuecomment-2998084736
     expected:
       if subsuite == "vello_canvas": FAIL
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/path-objects/2d.path.stroke.scale2.html.ini

@@ -2,3 +2,4 @@
   [Stroke line widths are scaled by the current transformation matrix]
     expected:
       if subsuite == "vello_canvas": FAIL
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/pixel-manipulation/2d.imageData.put.alpha.html.ini

@@ -0,0 +1,4 @@
+[2d.imageData.put.alpha.html]
+  [putImageData() puts non-solid image data correctly]
+    expected:
+      if subsuite == "vello_cpu_canvas": FAIL

tests/wpt/meta/html/canvas/element/pixel-manipulation/2d.imageData.put.unchanged.html.ini

@@ -1,4 +1,3 @@
 [2d.imageData.put.unchanged.html]
   [putImageData(getImageData(...), ...) has no effect]
-    expected:
-      if subsuite == "": FAIL
+    expected: FAIL

tests/wpt/vello_cpu_canvas_subsuite.json

@@ -0,0 +1,8 @@
+{
+  "vello_cpu_canvas": {
+     "config": {
+        "binary_args": ["--pref", "dom_canvas_vello_cpu_enabled"]
+     },
+     "include": ["/html/canvas/element"]
+  }
+}