Revert "Remove attach and detach glyph cache."

This reverts commit 61d56b92a4076f8afd644d015913641d691e39c8.

Reason for revert: broke gldft text

Original change's description:
> Remove attach and detach glyph cache.
> 
> BUG=skia:7515
> 
> Change-Id: Ib978e3cf4cfffdefe6453feb520e5e73684abf2e
> Reviewed-on: https://skia-review.googlesource.com/112560
> Reviewed-by: Ben Wagner <bungeman@google.com>
> Commit-Queue: Herb Derby <herb@google.com>

TBR=bungeman@google.com,herb@google.com

Change-Id: Id5723a3abcd103ed20197bba2dab06e8074be633
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:7515
Reviewed-on: https://skia-review.googlesource.com/112745
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Herb Derby <herb@google.com>
13 files changed