[includes] Remove include link between SkPathRef.h and SkRRect.h

According to go/chrome-includes [1], this will save about
40MB (0.02%) off the Chrome build. http://screen/4GnPjFaYpwCVHVL

I'm not quite sure why the link is so expensive, but we can
forward declare it and move the implementation from the .h
to the .cpp file easily enough.

[1] https://commondatastorage.googleapis.com/chromium-browser-clang/include-analysis.html#view=edges&filter=%5Ethird_party%2Fskia%2Finclude%2Fprivate%2FSkPathRef%5C.h%24&sort=includes&reverse=&includer=%5Ethird_party%2Fskia%2Finclude%2Fprivate%2FSkPathRef%5C.h%24&included=&limit=1000

Canary-Chromium-CL: 3485346
Change-Id: Ie3a5e7a735426f883a6c06ddbd3b8bf148bf1709
Bug: 242216
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/512158
Reviewed-by: Robert Phillips <robertphillips@google.com>
14 files changed