Change SkResourceCache to take a Visitor inside its find().

This reverts commit 595aa05efcb504e85358b8d328ac4a9fa1c46e2e.

BUG=skia:
R=mtklein@google.com, danakj@chromium.org

Author: reed@google.com

Review URL: https://codereview.chromium.org/569353002
5 files changed