This API can be used to back a view and its children with either a
software layer (bitmap) or hardware layer (FBO). Layers have
various usages, including color filtering and performance
improvements during animations.
Change-Id: Ifc3bea847918042730fc5a8c2d4206dd6c9420a3
Also created delegates for all missing shader, xfermode
and patheffect classes. Moved the logic of the xfermode,
and patheffects that was in Canvas_Delegate into the
xfermode/patheffect classes, and added support (in all
3 clases) for knowing if the shader/xfermode/patheffect
is actually supported or not. Make use of fidelityWarning
in LayoutLog if they are not.