Along with a dependent struct DirectDrawInfo.
This allows nsImageRenderer.h and CanvasRenderingContext2D.h to
avoid including nsLayoutUtils.h.
For nsImageRenderer.h in particular, a forward declaration is
not sufficient as nsImageRenderer stores SurfaceFromElementResult
by value.
A couple of method definitions elsewhere are moved out of line
to keep things compiling without including nsLayoutUtils.h in
additional headers.
Differential Revision: https://phabricator.services.mozilla.com/D91684