Revert of rename SkCanvasDrawable to SkDrawable, and make public (patchset #2 id...

Revert of rename SkCanvasDrawable to SkDrawable, and make public (patchset #2 id:20001 of https://codereview.chromium.org/903993002/)

Reason for revert:
bug in gyp

Original issue's description:
> rename SkCanvasDrawable to SkDrawable, and make public
>
> BUG=skia:
> NOTRY=True
> ... winbuilder flake
>
> Committed: https://skia.googlesource.com/skia/+/4ae9eb7463cf2160723407359608f221c0d5e2a6

TBR=robertphillips@google.com,djsollen@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/882853006