fonts: Cleanup cache miss logging for font remoting.

Add hooks to notify the embedder if there is a cache miss during draw.
Also remove the reference to SkStrikeClient from SkTypefaceProxy and
SkScalerContextProxy, since the proxies can outlive the client.

R=herb@google.com

Bug: 829622
Change-Id: Ib2fd1b91ebd057856c1d4e717cf50b49f08c903b
Reviewed-on: https://skia-review.googlesource.com/129402
Commit-Queue: Khusal Sagar <khushalsagar@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
5 files changed