Remove GrSurfaceDesc member from GrSurfaceProxy.

Remove GrSurfaceDesc member from GrSurfaceProxy.

Stores the config, origin, and dimensions in GrSurfaceProxy, sample count in GrRenderTargetProxy, and "was constructed with mip maps" in GrTextureProxy.

Change-Id: Iee058674dce49107a991cca9d083cd33e3572809
Reviewed-on: https://skia-review.googlesource.com/17209
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>