Invalidate path VBs when paths are destroyed

For this to work, we need access to the "original" path,
before any style was applied. To that end, add an original
path to GrShape (and unit tests of that functionality).

Then add a version of addGenIDChangeListener to GrShape,
that propagates to the original path, and use that in
tessellating path renderer.

Includes unit tests of caching behavior in the PR, all
of which failed without this change.

Bug: skia:
Change-Id: I98bb505f521e8ff07184f5c3fbd3c5fd1a22d3d5
Reviewed-on: https://skia-review.googlesource.com/50300
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
6 files changed