Rather than one monolithic file, we now have one monolithic
file (canvascontext2d) and several smaller files (one per class,
and some helpers).
This should make the code navigation a little easier.
Bug: skia:
Change-Id: Ia191c2db778591af21d2a6126f053c17c4f677f1
Reviewed-on: https://skia-review.googlesource.com/c/175996
Reviewed-by: Florin Malita <fmalita@chromium.org>
