This class is a RAII class that can be used to push a stacking context
with properties from a WebRenderLayer. It can also then be used to
convert rects in the layer coordinate system to be relative to the
stacking context, which is what we want for passing to WR.
MozReview-Commit-ID: 1WVrfRYqLqc
As we are often converting from LayoutDevicePixel to LayerPixel types
in WebRenderDisplayItem code, I added a convenience overload of
RelativeToParent that takes a LayoutDeviceRect and returns a LayerRect,
even though this is a potential footgun if abused.
MozReview-Commit-ID: DABAWdOBsbV
This extracts a strongly-typed ClipRect() function from GetWrClipRect.
GetWrClipRect is left as a weakly-typed wrapper for existing call sites,
and also does the necessary reference point conversions.
MozReview-Commit-ID: EuyzYIYLR6S
This moves the bulk of the meaningful work done by GetWrRelBounds into
strongly-typed helper functions. GetWrRelBounds is left as a wrapper so
call sites don't need to be updated yet. Note also that the
strongly-typed functions do not do any conversions from one reference
point from another (e.g. by calling the RelativeToXXX functions).
MozReview-Commit-ID: B3nPbOJOf9o
