Expand texturability testing to cover mip-mapped textures, and fix iOS

Don't allow creation of mip-mapped textures when caps says we don't
support mip-mapping.

Skip testing of mip-mapped resources in the resource size test,
when creation will fail.

For iOS devices with ES2, the APPLE BGRA8888 extension is more
trouble than it's worth. Even though it lets the internal and
external formats not match, it appears that the driver remembers
the first external format, so subsequent attempts to upload with
the other swizzle will fail. Up until now, creation of these
textures was failing anyway, so now just make it more explicit
that we don't support BGRA in this situation.

Re-land of: https://skia-review.googlesource.com/18261

BUG=skia:

Change-Id: I910ffab0aa735647dce910d9054696c385f94933
Reviewed-on: https://skia-review.googlesource.com/18382
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
5 files changed