Allow access to global glyph cache

The global glyph cache pointer is closed over in
SkStrikeCache.cpp. Allow access to it for future code
to move away from the global glyph cache.

BUG=skia:8091

Change-Id: I6e1fb712c082452e6a3b54f5fb5e6167caf9e757
Reviewed-on: https://skia-review.googlesource.com/136613
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
3 files changed