Add function to GrProxyProvider to lazily upload mip map data

Bug: skia:
Change-Id: I906207727242bed8a109bf3ca10b5a6e8e4b952e
Reviewed-on: https://skia-review.googlesource.com/104581
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
8 files changed