Add deferred count to GrResource.

This will be used to determine whether a resource can either be deleted or reinserted in the cache when its ref count reaches zero.
Review URL: https://codereview.appspot.com/7202046

git-svn-id: http://skia.googlecode.com/svn/trunk/include@7355 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed