If either of the two transform functions during interpolation is a 3D
function, both of them get coerced to a 3D function before deciding what
to do next. However, we only supported converting 2D functions to 3D if
they had a 2D primitive they could be converted to first.
Change our behavior to default to converting to matrix3d() if there is
no explicit conversion path. Fixes a crash in
`css/css-transforms/animation/transform-interpolation-004.html`.
We had a partial implementation of transformation function interpolation
that did not support numerical interpolation of simple functions (e.g.
`scale(0)` -> `scale(1)`). This refactors the interpolation to follow
the spec more closely.
Gains us 267 WPT subtest passes in `css/css-transforms`.
Fixes#6774.
The transform of each paintable was being applied multiple times due to
the recursive nature of the hit testing methods. Previously it used
combined_css_transform to transform the position, and then it would pass
that position to children, which would then apply combined_css_transform
again, and so on.
PaintableBoxes are also not hit tested anymore when having a stacking
context. A similar check is done in PaintableWithLines, but it was
missing from PaintableBox. Without this check some elements can get
returned multiple times from a hit test.
StackingContexts with zero opacity will now also get hit tested, as it
should have been before.
