Currently, the PDF backend does not support image filters (since PDF
does not have that functionality), so it simply removes them. This is
causing Chrome print preview to render incorrectly (see bug). The fix
here is to fall back to a raster device for image filters, as we used
to do in Blink. The resulting bitmap will be drawn to the destination
device as a normal main-memory-backed bitmap.
Note: this change invalidates the PDF results of all GMs containing
image filters (since they'll actually be rendered).
BUG=422144
Review URL: https://codereview.chromium.org/644323006
b0e89dcc1d