real fix for textblob use after gpu free

This patch addresses two issues:
1) Textblobs with abandoned strikes were not properly regenerating.
2) Provided by ericrk - GrTextBlobCache removed blobs from |fCache| during freeAll, but left
potentially released blobs in the |fBlobList|. We now remove these from
|fBlobList| as well.
BUG=skia:

Review URL: https://codereview.chromium.org/1160633002
4 files changed