This is essentially a reland of 9cf9bcbe

This code always allocates a new memory buffer for the texture memory,
picks a load function to copy/convert the input data into it, and the
uploads.

In the case where the input format matches the upload format we should
be able to skip the allocation and copy and be much happier.

Change-Id: If4281aeb4cd7bbbebba60122a10610a916833052
Reviewed-on: https://chromium-review.googlesource.com/326852
Tryjob-Request: John Bauman <jbauman@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: John Bauman <jbauman@chromium.org>